diff --git a/pagetop/src/base/component/block.rs b/pagetop/src/base/component/block.rs
index 99950286..86370ff4 100644
--- a/pagetop/src/base/component/block.rs
+++ b/pagetop/src/base/component/block.rs
@@ -13,12 +13,12 @@ pub struct Block {
 impl PageComponent for Block {
     fn new() -> Self {
         Block {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             components: PageContainer::new(),
-            title     : OptAttr::none(),
-            id        : OptIden::none(),
-            classes   : Classes::none(),
+            title     : OptAttr::new(),
+            id        : OptIden::new(),
+            classes   : Classes::new_with_default("block"),
             template  : "default".to_owned(),
         }
     }
@@ -34,7 +34,7 @@ impl PageComponent for Block {
     fn default_render(&self, assets: &mut PageAssets) -> Markup {
         let id = assets.serial_id(self.name(), self.id());
         html! {
-            div id=(id) class=[self.classes("block")] {
+            div id=(id) class=[self.classes()] {
                 @match self.title() {
                     Some(title) => h2 class="block-title" { (title) },
                     None => {}
@@ -63,36 +63,63 @@ impl Block {
     // Block BUILDER.
 
     pub fn with_renderable(mut self, renderable: fn() -> bool) -> Self {
-        self.renderable = renderable;
+        self.alter_renderable(renderable);
         self
     }
 
     pub fn with_weight(mut self, weight: i8) -> Self {
-        self.weight = weight;
+        self.alter_weight(weight);
         self
     }
 
     pub fn with_title(mut self, title: &str) -> Self {
-        self.title.with_value(title);
+        self.alter_title(title);
         self
     }
 
     pub fn with_id(mut self, id: &str) -> Self {
-        self.id.with_value(id);
+        self.alter_id(id);
         self
     }
 
-    pub fn set_classes(mut self, classes: &str) -> Self {
-        self.classes.set_classes(classes);
-        self
-    }
-
-    pub fn add_classes(mut self, classes: &str) -> Self {
-        self.classes.add_classes(classes);
+    pub fn with_classes(mut self, classes: &str, op: ClassesOp) -> Self {
+        self.alter_classes(classes, op);
         self
     }
 
     pub fn using_template(mut self, template: &str) -> Self {
+        self.alter_template(template);
+        self
+    }
+
+    // Block ALTER.
+
+    pub fn alter_renderable(&mut self, renderable: fn() -> bool) -> &mut Self {
+        self.renderable = renderable;
+        self
+    }
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
+        self.weight = weight;
+        self
+    }
+
+    pub fn alter_title(&mut self, title: &str) -> &mut Self {
+        self.title.with_value(title);
+        self
+    }
+
+    pub fn alter_id(&mut self, id: &str) -> &mut Self {
+        self.id.with_value(id);
+        self
+    }
+
+    pub fn alter_classes(&mut self, classes: &str, op: ClassesOp) -> &mut Self {
+        self.classes.alter(classes, op);
+        self
+    }
+
+    pub fn alter_template(&mut self, template: &str) -> &mut Self {
         self.template = template.to_owned();
         self
     }
@@ -107,15 +134,11 @@ impl Block {
         self.id.option()
     }
 
-    pub fn classes(&self, default: &str) -> Option<String> {
-        self.classes.option(default)
+    pub fn classes(&self) -> &Option<String> {
+        self.classes.option()
     }
 
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
 }
-
-fn always() -> bool {
-    true
-}
diff --git a/pagetop/src/base/component/chunck.rs b/pagetop/src/base/component/chunck.rs
index 0e46c779..6dbc0ff1 100644
--- a/pagetop/src/base/component/chunck.rs
+++ b/pagetop/src/base/component/chunck.rs
@@ -10,7 +10,7 @@ pub struct Chunck {
 impl PageComponent for Chunck {
     fn new() -> Self {
         Chunck {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             html      : html! {},
             template  : "default".to_owned(),
@@ -32,24 +32,49 @@ impl PageComponent for Chunck {
 
 impl Chunck {
     pub fn with(html: Markup) -> Self {
-        let mut chunck = Chunck::new();
-        chunck.html = html;
-        chunck
+        Chunck::new().with_html(html)
     }
 
     // Chunck BUILDER.
 
     pub fn with_renderable(mut self, renderable: fn() -> bool) -> Self {
-        self.renderable = renderable;
+        self.alter_renderable(renderable);
         self
     }
 
     pub fn with_weight(mut self, weight: i8) -> Self {
-        self.weight = weight;
+        self.alter_weight(weight);
+        self
+    }
+
+    pub fn with_html(mut self, html: Markup) -> Self {
+        self.alter_html(html);
         self
     }
 
     pub fn using_template(mut self, template: &str) -> Self {
+        self.alter_template(template);
+        self
+    }
+
+    // Chunck ALTER.
+
+    pub fn alter_renderable(&mut self, renderable: fn() -> bool) -> &mut Self {
+        self.renderable = renderable;
+        self
+    }
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
+        self.weight = weight;
+        self
+    }
+
+    pub fn alter_html(&mut self, html: Markup) -> &mut Self {
+        self.html = html;
+        self
+    }
+
+    pub fn alter_template(&mut self, template: &str) -> &mut Self {
         self.template = template.to_owned();
         self
     }
@@ -64,7 +89,3 @@ impl Chunck {
         self.template.as_str()
     }
 }
-
-fn always() -> bool {
-    true
-}
diff --git a/pagetop/src/base/component/container.rs b/pagetop/src/base/component/container.rs
index 70162bb9..fab8225a 100644
--- a/pagetop/src/base/component/container.rs
+++ b/pagetop/src/base/component/container.rs
@@ -3,25 +3,27 @@ use crate::prelude::*;
 pub enum ContainerType { Header, Footer, Main, Section, Wrapper }
 
 pub struct Container {
-    renderable: fn() -> bool,
-    weight    : i8,
-    components: PageContainer,
-    container : ContainerType,
-    id        : OptIden,
-    classes   : Classes,
-    template  : String,
+    renderable   : fn() -> bool,
+    weight       : i8,
+    components   : PageContainer,
+    container    : ContainerType,
+    id           : OptIden,
+    classes      : Classes,
+    inner_classes: Classes,
+    template     : String,
 }
 
 impl PageComponent for Container {
     fn new() -> Self {
         Container {
-            renderable: always,
-            weight    : 0,
-            components: PageContainer::new(),
-            container : ContainerType::Wrapper,
-            id        : OptIden::none(),
-            classes   : Classes::none(),
-            template  : "default".to_owned(),
+            renderable   : render_always,
+            weight       : 0,
+            components   : PageContainer::new(),
+            container    : ContainerType::Wrapper,
+            id           : OptIden::new(),
+            classes      : Classes::new_with_default("container"),
+            inner_classes: Classes::new_with_default("container"),
+            template     : "default".to_owned(),
         }
     }
 
@@ -36,35 +38,35 @@ impl PageComponent for Container {
     fn default_render(&self, assets: &mut PageAssets) -> Markup {
         match self.container_type() {
             ContainerType::Header => html! {
-                header id=[self.id()] class=[self.classes("header")] {
-                    div class="container" {
+                header id=[self.id()] class=[self.classes()] {
+                    div class=[self.inner_classes()] {
                         (self.components().render(assets))
                     }
                 }
             },
             ContainerType::Footer => html! {
-                footer id=[self.id()] class=[self.classes("footer")] {
-                    div class="container" {
+                footer id=[self.id()] class=[self.classes()] {
+                    div class=[self.inner_classes()] {
                         (self.components().render(assets))
                     }
                 }
             },
             ContainerType::Main => html! {
-                main id=[self.id()] class=[self.classes("main")] {
-                    div class="container" {
+                main id=[self.id()] class=[self.classes()] {
+                    div class=[self.inner_classes()] {
                         (self.components().render(assets))
                     }
                 }
             },
             ContainerType::Section => html! {
-                section id=[self.id()] class=[self.classes("section")] {
-                    div class="container" {
+                section id=[self.id()] class=[self.classes()] {
+                    div class=[self.inner_classes()] {
                         (self.components().render(assets))
                     }
                 }
             },
             _ => html! {
-                div id=[self.id()] class=[self.classes("container")] {
+                div id=[self.id()] class=[self.classes()] {
                     (self.components().render(assets))
                 }
             }
@@ -74,25 +76,25 @@ impl PageComponent for Container {
 
 impl Container {
     pub fn header() -> Self {
-        let mut c = Container::new();
+        let mut c = Container::new().with_classes("header", ClassesOp::SetDefault);
         c.container = ContainerType::Header;
         c
     }
 
     pub fn footer() -> Self {
-        let mut c = Container::new();
+        let mut c = Container::new().with_classes("footer", ClassesOp::SetDefault);
         c.container = ContainerType::Footer;
         c
     }
 
     pub fn main() -> Self {
-        let mut c = Container::new();
+        let mut c = Container::new().with_classes("main", ClassesOp::SetDefault);
         c.container = ContainerType::Main;
         c
     }
 
     pub fn section() -> Self {
-        let mut c = Container::new();
+        let mut c = Container::new().with_classes("section", ClassesOp::SetDefault);
         c.container = ContainerType::Section;
         c
     }
@@ -111,31 +113,63 @@ impl Container {
     // Container BUILDER.
 
     pub fn with_renderable(mut self, renderable: fn() -> bool) -> Self {
-        self.renderable = renderable;
+        self.alter_renderable(renderable);
         self
     }
 
     pub fn with_weight(mut self, weight: i8) -> Self {
-        self.weight = weight;
+        self.alter_weight(weight);
         self
     }
 
     pub fn with_id(mut self, id: &str) -> Self {
-        self.id.with_value(id);
+        self.alter_id(id);
         self
     }
 
-    pub fn set_classes(mut self, classes: &str) -> Self {
-        self.classes.set_classes(classes);
+    pub fn with_classes(mut self, classes: &str, op: ClassesOp) -> Self {
+        self.alter_classes(classes, op);
         self
     }
 
-    pub fn add_classes(mut self, classes: &str) -> Self {
-        self.classes.add_classes(classes);
+    pub fn with_inner_classes(mut self, classes: &str, op: ClassesOp) -> Self {
+        self.alter_inner_classes(classes, op);
         self
     }
 
     pub fn using_template(mut self, template: &str) -> Self {
+        self.alter_template(template);
+        self
+    }
+
+    // Container ALTER.
+
+    pub fn alter_renderable(&mut self, renderable: fn() -> bool) -> &mut Self {
+        self.renderable = renderable;
+        self
+    }
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
+        self.weight = weight;
+        self
+    }
+
+    pub fn alter_id(&mut self, id: &str) -> &mut Self {
+        self.id.with_value(id);
+        self
+    }
+
+    pub fn alter_classes(&mut self, classes: &str, op: ClassesOp) -> &mut Self {
+        self.classes.alter(classes, op);
+        self
+    }
+
+    pub fn alter_inner_classes(&mut self, classes: &str, op: ClassesOp) -> &mut Self {
+        self.inner_classes.alter(classes, op);
+        self
+    }
+
+    pub fn alter_template(&mut self, template: &str) -> &mut Self {
         self.template = template.to_owned();
         self
     }
@@ -150,15 +184,15 @@ impl Container {
         self.id.option()
     }
 
-    pub fn classes(&self, default: &str) -> Option<String> {
-        self.classes.option(default)
+    pub fn classes(&self) -> &Option<String> {
+        self.classes.option()
+    }
+
+    pub fn inner_classes(&self) -> &Option<String> {
+        self.inner_classes.option()
     }
 
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
 }
-
-fn always() -> bool {
-    true
-}
diff --git a/pagetop/src/base/component/form/button.rs b/pagetop/src/base/component/form/button.rs
index f99f06d3..4c75dc62 100644
--- a/pagetop/src/base/component/form/button.rs
+++ b/pagetop/src/base/component/form/button.rs
@@ -17,16 +17,17 @@ pub struct Button {
 impl PageComponent for Button {
     fn new() -> Self {
         Button {
-            renderable : always,
+            renderable : render_always,
             weight     : 0,
             button_type: ButtonType::Button,
-            name       : OptAttr::none(),
-            value      : OptAttr::none(),
-            autofocus  : OptAttr::none(),
-            disabled   : OptAttr::none(),
-            classes    : Classes::none(),
+            name       : OptAttr::new(),
+            value      : OptAttr::new(),
+            autofocus  : OptAttr::new(),
+            disabled   : OptAttr::new(),
+            classes    : Classes::new_with_default("btn btn-primary"),
             template   : "default".to_owned(),
         }
+        .with_classes("form-button", ClassesOp::AddFirst)
     }
 
     fn is_renderable(&self) -> bool {
@@ -38,10 +39,10 @@ impl PageComponent for Button {
     }
 
     fn default_render(&self, _: &mut PageAssets) -> Markup {
-        let (button_type, button_class) = match self.button_type() {
-            ButtonType::Button => ("button", "btn btn-primary form-button"),
-            ButtonType::Reset  => ("reset",  "btn btn-primary form-reset" ),
-            ButtonType::Submit => ("submit", "btn btn-primary form-submit"),
+        let button_type = match self.button_type() {
+            ButtonType::Button => "button",
+            ButtonType::Reset  => "reset",
+            ButtonType::Submit => "submit",
         };
         let id = match self.name() {
             Some(name) => Some(concat_string!("edit-", name)),
@@ -51,7 +52,7 @@ impl PageComponent for Button {
             button
                 type=(button_type)
                 id=[id]
-                class=[self.classes(button_class)]
+                class=[self.classes()]
                 name=[self.name()]
                 value=[self.value()]
                 autofocus=[self.autofocus()]
@@ -72,13 +73,17 @@ impl Button {
     }
 
     pub fn reset(value: &str) -> Self {
-        let mut button = Button::new().with_value(value);
+        let mut button = Button::new()
+            .with_classes("form-reset", ClassesOp::Replace("form-button"))
+            .with_value(value);
         button.button_type = ButtonType::Reset;
         button
     }
 
     pub fn submit(value: &str) -> Self {
-        let mut button = Button::new().with_value(value);
+        let mut button = Button::new()
+            .with_classes("form-submit", ClassesOp::Replace("form-button"))
+            .with_value(value);
         button.button_type = ButtonType::Submit;
         button
     }
@@ -86,26 +91,68 @@ impl Button {
     // Button BUILDER.
 
     pub fn with_renderable(mut self, renderable: fn() -> bool) -> Self {
-        self.renderable = renderable;
+        self.alter_renderable(renderable);
         self
     }
 
     pub fn with_weight(mut self, weight: i8) -> Self {
-        self.weight = weight;
+        self.alter_weight(weight);
         self
     }
 
     pub fn with_name(mut self, name: &str) -> Self {
-        self.name.with_value(name);
+        self.alter_name(name);
         self
     }
 
     pub fn with_value(mut self, value: &str) -> Self {
-        self.value.with_value(value);
+        self.alter_value(value);
         self
     }
 
     pub fn with_autofocus(mut self, toggle: bool) -> Self {
+        self.alter_autofocus(toggle);
+        self
+    }
+
+    pub fn with_disabled(mut self, toggle: bool) -> Self {
+        self.alter_disabled(toggle);
+        self
+    }
+
+    pub fn with_classes(mut self, classes: &str, op: ClassesOp) -> Self {
+        self.alter_classes(classes, op);
+        self
+    }
+
+    pub fn using_template(mut self, template: &str) -> Self {
+        self.alter_template(template);
+        self
+    }
+
+    // Button ALTER.
+
+    pub fn alter_renderable(&mut self, renderable: fn() -> bool) -> &mut Self {
+        self.renderable = renderable;
+        self
+    }
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
+        self.weight = weight;
+        self
+    }
+
+    pub fn alter_name(&mut self, name: &str) -> &mut Self {
+        self.name.with_value(name);
+        self
+    }
+
+    pub fn alter_value(&mut self, value: &str) -> &mut Self {
+        self.value.with_value(value);
+        self
+    }
+
+    pub fn alter_autofocus(&mut self, toggle: bool) -> &mut Self {
         self.autofocus.with_value(match toggle {
             true => "autofocus",
             false => "",
@@ -113,7 +160,7 @@ impl Button {
         self
     }
 
-    pub fn with_disabled(mut self, toggle: bool) -> Self {
+    pub fn alter_disabled(&mut self, toggle: bool) -> &mut Self {
         self.disabled.with_value(match toggle {
             true => "disabled",
             false => "",
@@ -121,17 +168,12 @@ impl Button {
         self
     }
 
-    pub fn set_classes(mut self, classes: &str) -> Self {
-        self.classes.set_classes(classes);
+    pub fn alter_classes(&mut self, classes: &str, op: ClassesOp) -> &mut Self {
+        self.classes.alter(classes, op);
         self
     }
 
-    pub fn add_classes(mut self, classes: &str) -> Self {
-        self.classes.add_classes(classes);
-        self
-    }
-
-    pub fn using_template(mut self, template: &str) -> Self {
+    pub fn alter_template(&mut self, template: &str) -> &mut Self {
         self.template = template.to_owned();
         self
     }
@@ -158,15 +200,11 @@ impl Button {
         self.disabled.option()
     }
 
-    pub fn classes(&self, default: &str) -> Option<String> {
-        self.classes.option(default)
+    pub fn classes(&self) -> &Option<String> {
+        self.classes.option()
     }
 
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
 }
-
-fn always() -> bool {
-    true
-}
diff --git a/pagetop/src/base/component/form/date.rs b/pagetop/src/base/component/form/date.rs
index 40c2f784..10e795cb 100644
--- a/pagetop/src/base/component/form/date.rs
+++ b/pagetop/src/base/component/form/date.rs
@@ -20,21 +20,22 @@ pub struct Date {
 impl PageComponent for Date {
     fn new() -> Self {
         Date {
-            renderable  : always,
+            renderable  : render_always,
             weight      : 0,
-            name        : OptAttr::none(),
-            value       : OptAttr::none(),
-            label       : OptAttr::none(),
-            placeholder : OptAttr::none(),
-            autofocus   : OptAttr::none(),
-            autocomplete: OptAttr::none(),
-            disabled    : OptAttr::none(),
-            readonly    : OptAttr::none(),
-            required    : OptAttr::none(),
-            help_text   : OptAttr::none(),
-            classes     : Classes::none(),
+            name        : OptAttr::new(),
+            value       : OptAttr::new(),
+            label       : OptAttr::new(),
+            placeholder : OptAttr::new(),
+            autofocus   : OptAttr::new(),
+            autocomplete: OptAttr::new(),
+            disabled    : OptAttr::new(),
+            readonly    : OptAttr::new(),
+            required    : OptAttr::new(),
+            help_text   : OptAttr::new(),
+            classes     : Classes::new_with_default("form-item"),
             template    : "default".to_owned(),
         }
+        .with_classes("form-type-date", ClassesOp::AddFirst)
     }
 
     fn is_renderable(&self) -> bool {
@@ -46,18 +47,12 @@ impl PageComponent for Date {
     }
 
     fn default_render(&self, _: &mut PageAssets) -> Markup {
-        let (classes, id) = match self.name() {
-            Some(name) => (
-                concat_string!("form-item form-item-", name, " form-type-date"),
-                Some(concat_string!("edit-", name))
-            ),
-            None => (
-                "form-item form-type-date".to_owned(),
-                None
-            )
+        let id = match self.name() {
+            Some(name) => Some(concat_string!("edit-", name)),
+            None => None,
         };
         html! {
-            div class=[self.classes(classes.as_str())] {
+            div class=[self.classes()] {
                 @match self.label() {
                     Some(label) => label class="form-label" for=[&id] {
                         (label) " "
@@ -96,36 +91,108 @@ impl Date {
     // Date BUILDER.
 
     pub fn with_renderable(mut self, renderable: fn() -> bool) -> Self {
-        self.renderable = renderable;
+        self.alter_renderable(renderable);
         self
     }
 
     pub fn with_weight(mut self, weight: i8) -> Self {
-        self.weight = weight;
+        self.alter_weight(weight);
         self
     }
 
     pub fn with_name(mut self, name: &str) -> Self {
-        self.name.with_value(name);
+        self.alter_name(name);
         self
     }
 
     pub fn with_value(mut self, value: &str) -> Self {
-        self.value.with_value(value);
+        self.alter_value(value);
         self
     }
 
     pub fn with_label(mut self, label: &str) -> Self {
-        self.label.with_value(label);
+        self.alter_label(label);
         self
     }
 
     pub fn with_placeholder(mut self, placeholder: &str) -> Self {
-        self.placeholder.with_value(placeholder);
+        self.alter_placeholder(placeholder);
         self
     }
 
     pub fn with_autofocus(mut self, toggle: bool) -> Self {
+        self.alter_autofocus(toggle);
+        self
+    }
+
+    pub fn with_autocomplete(mut self, toggle: bool) -> Self {
+        self.alter_autocomplete(toggle);
+        self
+    }
+
+    pub fn with_disabled(mut self, toggle: bool) -> Self {
+        self.alter_disabled(toggle);
+        self
+    }
+
+    pub fn with_readonly(mut self, toggle: bool) -> Self {
+        self.alter_readonly(toggle);
+        self
+    }
+
+    pub fn with_required(mut self, toggle: bool) -> Self {
+        self.alter_required(toggle);
+        self
+    }
+
+    pub fn with_help_text(mut self, help_text: &str) -> Self {
+        self.alter_help_text(help_text);
+        self
+    }
+
+    pub fn with_classes(mut self, classes: &str, op: ClassesOp) -> Self {
+        self.alter_classes(classes, op);
+        self
+    }
+
+    pub fn using_template(mut self, template: &str) -> Self {
+        self.alter_template(template);
+        self
+    }
+
+    // Date ALTER.
+
+    pub fn alter_renderable(&mut self, renderable: fn() -> bool) -> &mut Self {
+        self.renderable = renderable;
+        self
+    }
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
+        self.weight = weight;
+        self
+    }
+
+    pub fn alter_name(&mut self, name: &str) -> &mut Self {
+        self.name.with_value(name);
+        self
+    }
+
+    pub fn alter_value(&mut self, value: &str) -> &mut Self {
+        self.value.with_value(value);
+        self
+    }
+
+    pub fn alter_label(&mut self, label: &str) -> &mut Self {
+        self.label.with_value(label);
+        self
+    }
+
+    pub fn alter_placeholder(&mut self, placeholder: &str) -> &mut Self {
+        self.placeholder.with_value(placeholder);
+        self
+    }
+
+    pub fn alter_autofocus(&mut self, toggle: bool) -> &mut Self {
         self.autofocus.with_value(match toggle {
             true => "autofocus",
             false => "",
@@ -133,7 +200,7 @@ impl Date {
         self
     }
 
-    pub fn with_autocomplete(mut self, toggle: bool) -> Self {
+    pub fn alter_autocomplete(&mut self, toggle: bool) -> &mut Self {
         self.autocomplete.with_value(match toggle {
             true => "",
             false => "off",
@@ -141,7 +208,7 @@ impl Date {
         self
     }
 
-    pub fn with_disabled(mut self, toggle: bool) -> Self {
+    pub fn alter_disabled(&mut self, toggle: bool) -> &mut Self {
         self.disabled.with_value(match toggle {
             true => "disabled",
             false => "",
@@ -149,7 +216,7 @@ impl Date {
         self
     }
 
-    pub fn with_readonly(mut self, toggle: bool) -> Self {
+    pub fn alter_readonly(&mut self, toggle: bool) -> &mut Self {
         self.readonly.with_value(match toggle {
             true => "readonly",
             false => "",
@@ -157,7 +224,7 @@ impl Date {
         self
     }
 
-    pub fn with_required(mut self, toggle: bool) -> Self {
+    pub fn alter_required(&mut self, toggle: bool) -> &mut Self {
         self.required.with_value(match toggle {
             true => "required",
             false => "",
@@ -165,22 +232,17 @@ impl Date {
         self
     }
 
-    pub fn with_help_text(mut self, help_text: &str) -> Self {
+    pub fn alter_help_text(&mut self, help_text: &str) -> &mut Self {
         self.help_text.with_value(help_text);
         self
     }
 
-    pub fn set_classes(mut self, classes: &str) -> Self {
-        self.classes.set_classes(classes);
+    pub fn alter_classes(&mut self, classes: &str, op: ClassesOp) -> &mut Self {
+        self.classes.alter(classes, op);
         self
     }
 
-    pub fn add_classes(mut self, classes: &str) -> Self {
-        self.classes.add_classes(classes);
-        self
-    }
-
-    pub fn using_template(mut self, template: &str) -> Self {
+    pub fn alter_template(&mut self, template: &str) -> &mut Self {
         self.template = template.to_owned();
         self
     }
@@ -227,15 +289,11 @@ impl Date {
         self.help_text.option()
     }
 
-    pub fn classes(&self, default: &str) -> Option<String> {
-        self.classes.option(default)
+    pub fn classes(&self) -> &Option<String> {
+        self.classes.option()
     }
 
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
 }
-
-fn always() -> bool {
-    true
-}
diff --git a/pagetop/src/base/component/form/form.rs b/pagetop/src/base/component/form/form.rs
index 07cb6e17..73581ca2 100644
--- a/pagetop/src/base/component/form/form.rs
+++ b/pagetop/src/base/component/form/form.rs
@@ -17,14 +17,14 @@ pub struct Form {
 impl PageComponent for Form {
     fn new() -> Self {
         Form {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             elements  : PageContainer::new(),
-            action    : OptAttr::none(),
-            charset   : OptAttr::some("UTF-8"),
+            action    : OptAttr::new(),
+            charset   : OptAttr::new_with_value("UTF-8"),
             method    : FormMethod::Post,
-            id        : OptIden::none(),
-            classes   : Classes::none(),
+            id        : OptIden::new(),
+            classes   : Classes::new_with_default("form"),
             template  : "default".to_owned(),
         }
     }
@@ -45,7 +45,7 @@ impl PageComponent for Form {
         html! {
             form
                 id=[self.id()]
-                class=[self.classes("form")]
+                class=[self.classes()]
                 action=[self.action()]
                 method=[method]
                 accept-charset=[self.charset()]
@@ -72,46 +72,83 @@ impl Form {
     // Form BUILDER.
 
     pub fn with_renderable(mut self, renderable: fn() -> bool) -> Self {
-        self.renderable = renderable;
+        self.alter_renderable(renderable);
         self
     }
 
     pub fn with_weight(mut self, weight: i8) -> Self {
-        self.weight = weight;
+        self.alter_weight(weight);
         self
     }
 
     pub fn with_action(mut self, action: &str) -> Self {
-        self.action.with_value(action);
+        self.alter_action(action);
         self
     }
 
     pub fn with_charset(mut self, charset: &str) -> Self {
-        self.charset.with_value(charset);
+        self.alter_charset(charset);
         self
     }
 
     pub fn with_method(mut self, method: FormMethod) -> Self {
-        self.method = method;
+        self.alter_method(method);
         self
     }
 
     pub fn with_id(mut self, id: &str) -> Self {
-        self.id.with_value(id);
+        self.alter_id(id);
         self
     }
 
-    pub fn set_classes(mut self, classes: &str) -> Self {
-        self.classes.set_classes(classes);
-        self
-    }
-
-    pub fn add_classes(mut self, classes: &str) -> Self {
-        self.classes.add_classes(classes);
+    pub fn with_classes(mut self, classes: &str, op: ClassesOp) -> Self {
+        self.alter_classes(classes, op);
         self
     }
 
     pub fn using_template(mut self, template: &str) -> Self {
+        self.alter_template(template);
+        self
+    }
+
+    // Form ALTER.
+
+    pub fn alter_renderable(&mut self, renderable: fn() -> bool) -> &mut Self {
+        self.renderable = renderable;
+        self
+    }
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
+        self.weight = weight;
+        self
+    }
+
+    pub fn alter_action(&mut self, action: &str) -> &mut Self {
+        self.action.with_value(action);
+        self
+    }
+
+    pub fn alter_charset(&mut self, charset: &str) -> &mut Self {
+        self.charset.with_value(charset);
+        self
+    }
+
+    pub fn alter_method(&mut self, method: FormMethod) -> &mut Self {
+        self.method = method;
+        self
+    }
+
+    pub fn alter_id(&mut self, id: &str) -> &mut Self {
+        self.id.with_value(id);
+        self
+    }
+
+    pub fn alter_classes(&mut self, classes: &str, op: ClassesOp) -> &mut Self {
+        self.classes.alter(classes, op);
+        self
+    }
+
+    pub fn alter_template(&mut self, template: &str) -> &mut Self {
         self.template = template.to_owned();
         self
     }
@@ -134,15 +171,11 @@ impl Form {
         self.id.option()
     }
 
-    pub fn classes(&self, default: &str) -> Option<String> {
-        self.classes.option(default)
+    pub fn classes(&self) -> &Option<String> {
+        self.classes.option()
     }
 
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
 }
-
-fn always() -> bool {
-    true
-}
diff --git a/pagetop/src/base/component/form/hidden.rs b/pagetop/src/base/component/form/hidden.rs
index 8f2cc4b3..736aa4ce 100644
--- a/pagetop/src/base/component/form/hidden.rs
+++ b/pagetop/src/base/component/form/hidden.rs
@@ -10,8 +10,8 @@ impl PageComponent for Hidden {
     fn new() -> Self {
         Hidden {
             weight: 0,
-            name  : OptIden::none(),
-            value : OptAttr::none(),
+            name  : OptIden::new(),
+            value : OptAttr::new(),
         }
     }
 
@@ -32,24 +32,39 @@ impl PageComponent for Hidden {
 
 impl Hidden {
     pub fn set(name: &str, value: &str) -> Self {
-        Hidden::new()
-            .with_name(name)
-            .with_value(value)
+        Hidden::new().with_name(name).with_value(value)
     }
 
     // Hidden BUILDER.
 
     pub fn with_weight(mut self, weight: i8) -> Self {
-        self.weight = weight;
+        self.alter_weight(weight);
         self
     }
 
     pub fn with_name(mut self, name: &str) -> Self {
-        self.name.with_value(name);
+        self.alter_name(name);
         self
     }
 
     pub fn with_value(mut self, value: &str) -> Self {
+        self.alter_value(value);
+        self
+    }
+
+    // Hidden ALTER.
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
+        self.weight = weight;
+        self
+    }
+
+    pub fn alter_name(&mut self, name: &str) -> &mut Self {
+        self.name.with_value(name);
+        self
+    }
+
+    pub fn alter_value(&mut self, value: &str) -> &mut Self {
         self.value.with_value(value);
         self
     }
diff --git a/pagetop/src/base/component/form/input.rs b/pagetop/src/base/component/form/input.rs
index 9d6e1afd..71d801b7 100644
--- a/pagetop/src/base/component/form/input.rs
+++ b/pagetop/src/base/component/form/input.rs
@@ -26,25 +26,26 @@ pub struct Input {
 impl PageComponent for Input {
     fn new() -> Self {
         Input {
-            renderable  : always,
+            renderable  : render_always,
             weight      : 0,
             input_type  : InputType::Textfield,
-            name        : OptIden::none(),
-            value       : OptAttr::none(),
-            label       : OptAttr::none(),
+            name        : OptIden::new(),
+            value       : OptAttr::new(),
+            label       : OptAttr::new(),
             size        : Some(60),
             minlength   : None,
             maxlength   : Some(128),
-            placeholder : OptAttr::none(),
-            autofocus   : OptAttr::none(),
-            autocomplete: OptAttr::none(),
-            disabled    : OptAttr::none(),
-            readonly    : OptAttr::none(),
-            required    : OptAttr::none(),
-            help_text   : OptAttr::none(),
-            classes     : Classes::none(),
+            placeholder : OptAttr::new(),
+            autofocus   : OptAttr::new(),
+            autocomplete: OptAttr::new(),
+            disabled    : OptAttr::new(),
+            readonly    : OptAttr::new(),
+            required    : OptAttr::new(),
+            help_text   : OptAttr::new(),
+            classes     : Classes::new_with_default("form-item"),
             template    : "default".to_owned(),
         }
+        .with_classes("form-type-textfield", ClassesOp::AddFirst)
     }
 
     fn is_renderable(&self) -> bool {
@@ -55,27 +56,28 @@ impl PageComponent for Input {
         self.weight
     }
 
+    fn before_render(&mut self, _: &mut PageAssets) {
+        if let Some(name) = self.name() {
+            let class = concat_string!("form-item-", name);
+            self.alter_classes(class.as_str(), ClassesOp::AddFirst);
+        }
+    }
+
     fn default_render(&self, _: &mut PageAssets) -> Markup {
-        let (type_input, type_class) = match self.input_type() {
-            InputType::Email     => ("email",    "form-type-email"),
-            InputType::Password  => ("password", "form-type-password"),
-            InputType::Search    => ("search",   "form-type-search"),
-            InputType::Telephone => ("tel",      "form-type-telephone"),
-            InputType::Textfield => ("text",     "form-type-textfield"),
-            InputType::Url       => ("url",      "form-type-url")
+        let type_input = match self.input_type() {
+            InputType::Email     => "email",
+            InputType::Password  => "password",
+            InputType::Search    => "search",
+            InputType::Telephone => "tel",
+            InputType::Textfield => "text",
+            InputType::Url       => "url",
         };
-        let (class, id) = match self.name() {
-            Some(name) => (
-                concat_string!("form-item form-item-", name, " ", type_class),
-                Some(concat_string!("edit-", name))
-            ),
-            None => (
-                concat_string!("form-item ", type_class),
-                None
-            )
+        let id = match self.name() {
+            Some(name) => Some(concat_string!("edit-", name)),
+            None => None,
         };
         html! {
-            div class=(class) {
+            div class=[self.classes()] {
                 @match self.label() {
                     Some(label) => label class="form-label" for=[&id] {
                         (label) " "
@@ -118,31 +120,36 @@ impl Input {
     }
 
     pub fn password() -> Self {
-        let mut input = Input::new();
+        let mut input = Input::new()
+            .with_classes("form-type-password", ClassesOp::Replace("form-type-textfield"));
         input.input_type = InputType::Password;
         input
     }
 
     pub fn search() -> Self {
-        let mut input = Input::new();
+        let mut input = Input::new()
+            .with_classes("form-type-search", ClassesOp::Replace("form-type-textfield"));
         input.input_type = InputType::Search;
         input
     }
 
     pub fn email() -> Self {
-        let mut input = Input::new();
+        let mut input = Input::new()
+            .with_classes("form-type-email", ClassesOp::Replace("form-type-textfield"));
         input.input_type = InputType::Email;
         input
     }
 
     pub fn telephone() -> Self {
-        let mut input = Input::new();
+        let mut input = Input::new()
+            .with_classes("form-type-telephone", ClassesOp::Replace("form-type-textfield"));
         input.input_type = InputType::Telephone;
         input
     }
 
     pub fn url() -> Self {
-        let mut input = Input::new();
+        let mut input = Input::new()
+            .with_classes("form-type-url", ClassesOp::Replace("form-type-textfield"));
         input.input_type = InputType::Url;
         input
     }
@@ -150,51 +157,138 @@ impl Input {
     // Input BUILDER.
 
     pub fn with_renderable(mut self, renderable: fn() -> bool) -> Self {
-        self.renderable = renderable;
+        self.alter_renderable(renderable);
         self
     }
 
     pub fn with_weight(mut self, weight: i8) -> Self {
-        self.weight = weight;
+        self.alter_weight(weight);
         self
     }
 
     pub fn with_name(mut self, name: &str) -> Self {
-        self.name.with_value(name);
+        self.alter_name(name);
         self
     }
 
     pub fn with_value(mut self, value: &str) -> Self {
-        self.value.with_value(value);
+        self.alter_value(value);
         self
     }
 
     pub fn with_label(mut self, label: &str) -> Self {
-        self.label.with_value(label);
+        self.alter_label(label);
         self
     }
 
     pub fn with_size(mut self, size: Option<u16>) -> Self {
-        self.size = size;
+        self.alter_size(size);
         self
     }
 
     pub fn with_minlength(mut self, minlength: Option<u16>) -> Self {
-        self.minlength = minlength;
+        self.alter_minlength(minlength);
         self
     }
 
     pub fn with_maxlength(mut self, maxlength: Option<u16>) -> Self {
-        self.maxlength = maxlength;
+        self.alter_maxlength(maxlength);
         self
     }
 
     pub fn with_placeholder(mut self, placeholder: &str) -> Self {
-        self.placeholder.with_value(placeholder);
+        self.alter_placeholder(placeholder);
         self
     }
 
     pub fn with_autofocus(mut self, toggle: bool) -> Self {
+        self.alter_autofocus(toggle);
+        self
+    }
+
+    pub fn with_autocomplete(mut self, toggle: bool) -> Self {
+        self.alter_autocomplete(toggle);
+        self
+    }
+
+    pub fn with_disabled(mut self, toggle: bool) -> Self {
+        self.alter_disabled(toggle);
+        self
+    }
+
+    pub fn with_readonly(mut self, toggle: bool) -> Self {
+        self.alter_readonly(toggle);
+        self
+    }
+
+    pub fn with_required(mut self, toggle: bool) -> Self {
+        self.alter_required(toggle);
+        self
+    }
+
+    pub fn with_help_text(mut self, help_text: &str) -> Self {
+        self.alter_help_text(help_text);
+        self
+    }
+
+    pub fn with_classes(mut self, classes: &str, op: ClassesOp) -> Self {
+        self.alter_classes(classes, op);
+        self
+    }
+
+    pub fn using_template(mut self, template: &str) -> Self {
+        self.alter_template(template);
+        self
+    }
+
+    // Input ALTER.
+
+    pub fn alter_renderable(&mut self, renderable: fn() -> bool) -> &mut Self {
+        self.renderable = renderable;
+        self
+    }
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
+        self.weight = weight;
+        self
+    }
+
+    pub fn alter_name(&mut self, name: &str) -> &mut Self {
+        self.name.with_value(name);
+        self
+    }
+
+    pub fn alter_value(&mut self, value: &str) -> &mut Self {
+        self.value.with_value(value);
+        self
+    }
+
+    pub fn alter_label(&mut self, label: &str) -> &mut Self {
+        self.label.with_value(label);
+        self
+    }
+
+    pub fn alter_size(&mut self, size: Option<u16>) -> &mut Self {
+        self.size = size;
+        self
+    }
+
+    pub fn alter_minlength(&mut self, minlength: Option<u16>) -> &mut Self {
+        self.minlength = minlength;
+        self
+    }
+
+    pub fn alter_maxlength(&mut self, maxlength: Option<u16>) -> &mut Self {
+        self.maxlength = maxlength;
+        self
+    }
+
+    pub fn alter_placeholder(&mut self, placeholder: &str) -> &mut Self {
+        self.placeholder.with_value(placeholder);
+        self
+    }
+
+    pub fn alter_autofocus(&mut self, toggle: bool) -> &mut Self {
         self.autofocus.with_value(match toggle {
             true => "autofocus",
             false => "",
@@ -202,7 +296,7 @@ impl Input {
         self
     }
 
-    pub fn with_autocomplete(mut self, toggle: bool) -> Self {
+    pub fn alter_autocomplete(&mut self, toggle: bool) -> &mut Self {
         self.autocomplete.with_value(match toggle {
             true => "",
             false => "off",
@@ -210,7 +304,7 @@ impl Input {
         self
     }
 
-    pub fn with_disabled(mut self, toggle: bool) -> Self {
+    pub fn alter_disabled(&mut self, toggle: bool) -> &mut Self {
         self.disabled.with_value(match toggle {
             true => "disabled",
             false => "",
@@ -218,7 +312,7 @@ impl Input {
         self
     }
 
-    pub fn with_readonly(mut self, toggle: bool) -> Self {
+    pub fn alter_readonly(&mut self, toggle: bool) -> &mut Self {
         self.readonly.with_value(match toggle {
             true => "readonly",
             false => "",
@@ -226,7 +320,7 @@ impl Input {
         self
     }
 
-    pub fn with_required(mut self, toggle: bool) -> Self {
+    pub fn alter_required(&mut self, toggle: bool) -> &mut Self {
         self.required.with_value(match toggle {
             true => "required",
             false => "",
@@ -234,22 +328,17 @@ impl Input {
         self
     }
 
-    pub fn with_help_text(mut self, help_text: &str) -> Self {
+    pub fn alter_help_text(&mut self, help_text: &str) -> &mut Self {
         self.help_text.with_value(help_text);
         self
     }
 
-    pub fn set_classes(mut self, classes: &str) -> Self {
-        self.classes.set_classes(classes);
+    pub fn alter_classes(&mut self, classes: &str, op: ClassesOp) -> &mut Self {
+        self.classes.alter(classes, op);
         self
     }
 
-    pub fn add_classes(mut self, classes: &str) -> Self {
-        self.classes.add_classes(classes);
-        self
-    }
-
-    pub fn using_template(mut self, template: &str) -> Self {
+    pub fn alter_template(&mut self, template: &str) -> &mut Self {
         self.template = template.to_owned();
         self
     }
@@ -312,15 +401,11 @@ impl Input {
         self.help_text.option()
     }
 
-    pub fn classes(&self, default: &str) -> Option<String> {
-        self.classes.option(default)
+    pub fn classes(&self) -> &Option<String> {
+        self.classes.option()
     }
 
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
 }
-
-fn always() -> bool {
-    true
-}
diff --git a/pagetop/src/base/component/grid/column.rs b/pagetop/src/base/component/grid/column.rs
index f29544ca..77512ea2 100644
--- a/pagetop/src/base/component/grid/column.rs
+++ b/pagetop/src/base/component/grid/column.rs
@@ -12,11 +12,11 @@ pub struct Column {
 impl PageComponent for Column {
     fn new() -> Self {
         Column {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             components: PageContainer::new(),
-            id        : OptIden::none(),
-            classes   : Classes::none(),
+            id        : OptIden::new(),
+            classes   : Classes::new_with_default("col"),
             template  : "default".to_owned(),
         }
     }
@@ -35,7 +35,7 @@ impl PageComponent for Column {
 
     fn default_render(&self, assets: &mut PageAssets) -> Markup {
         html! {
-            div id=[self.id()] class=[self.classes("col")] {
+            div id=[self.id()] class=[self.classes()] {
                 (self.components().render(assets))
             }
         }
@@ -58,31 +58,53 @@ impl Column {
     // Column BUILDER.
 
     pub fn with_renderable(mut self, renderable: fn() -> bool) -> Self {
-        self.renderable = renderable;
+        self.alter_renderable(renderable);
         self
     }
 
     pub fn with_weight(mut self, weight: i8) -> Self {
-        self.weight = weight;
+        self.alter_weight(weight);
         self
     }
 
     pub fn with_id(mut self, id: &str) -> Self {
-        self.id.with_value(id);
+        self.alter_id(id);
         self
     }
 
-    pub fn set_classes(mut self, classes: &str) -> Self {
-        self.classes.set_classes(classes);
-        self
-    }
-
-    pub fn add_classes(mut self, classes: &str) -> Self {
-        self.classes.add_classes(classes);
+    pub fn with_classes(mut self, classes: &str, op: ClassesOp) -> Self {
+        self.alter_classes(classes, op);
         self
     }
 
     pub fn using_template(mut self, template: &str) -> Self {
+        self.alter_template(template);
+        self
+    }
+
+    // Column ALTER.
+
+    pub fn alter_renderable(&mut self, renderable: fn() -> bool) -> &mut Self {
+        self.renderable = renderable;
+        self
+    }
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
+        self.weight = weight;
+        self
+    }
+
+    pub fn alter_id(&mut self, id: &str) -> &mut Self {
+        self.id.with_value(id);
+        self
+    }
+
+    pub fn alter_classes(&mut self, classes: &str, op: ClassesOp) -> &mut Self {
+        self.classes.alter(classes, op);
+        self
+    }
+
+    pub fn alter_template(&mut self, template: &str) -> &mut Self {
         self.template = template.to_owned();
         self
     }
@@ -93,15 +115,11 @@ impl Column {
         self.id.option()
     }
 
-    pub fn classes(&self, default: &str) -> Option<String> {
-        self.classes.option(default)
+    pub fn classes(&self) -> &Option<String> {
+        self.classes.option()
     }
 
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
 }
-
-fn always() -> bool {
-    true
-}
diff --git a/pagetop/src/base/component/grid/row.rs b/pagetop/src/base/component/grid/row.rs
index 96d74afc..4574b090 100644
--- a/pagetop/src/base/component/grid/row.rs
+++ b/pagetop/src/base/component/grid/row.rs
@@ -12,11 +12,11 @@ pub struct Row {
 impl PageComponent for Row {
     fn new() -> Self {
         Row {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             columns   : PageContainer::new(),
-            id        : OptIden::none(),
-            classes   : Classes::none(),
+            id        : OptIden::new(),
+            classes   : Classes::new_with_default("row"),
             template  : "default".to_owned(),
         }
     }
@@ -35,7 +35,7 @@ impl PageComponent for Row {
 
     fn default_render(&self, assets: &mut PageAssets) -> Markup {
         html! {
-            div id=[self.id()] class=[self.classes("row")] {
+            div id=[self.id()] class=[self.classes()] {
                 (self.columns().render(assets))
             }
         }
@@ -58,36 +58,53 @@ impl Row {
     // Row BUILDER.
 
     pub fn with_renderable(mut self, renderable: fn() -> bool) -> Self {
-        self.renderable = renderable;
+        self.alter_renderable(renderable);
         self
     }
 
     pub fn with_weight(mut self, weight: i8) -> Self {
-        self.weight = weight;
+        self.alter_weight(weight);
         self
     }
 
     pub fn with_id(mut self, id: &str) -> Self {
-        self.id.with_value(id);
+        self.alter_id(id);
         self
     }
 
-    pub fn set_classes(mut self, classes: &str) -> Self {
-        self.classes.set_classes(classes);
-        self
-    }
-
-    pub fn set_classes_ref(&mut self, classes: &str) -> &Self {
-        self.classes.set_classes(classes);
-        self
-    }
-
-    pub fn add_classes(mut self, classes: &str) -> Self {
-        self.classes.add_classes(classes);
+    pub fn with_classes(mut self, classes: &str, op: ClassesOp) -> Self {
+        self.alter_classes(classes, op);
         self
     }
 
     pub fn using_template(mut self, template: &str) -> Self {
+        self.alter_template(template);
+        self
+    }
+
+    // Row ALTER.
+
+    pub fn alter_renderable(&mut self, renderable: fn() -> bool) -> &mut Self {
+        self.renderable = renderable;
+        self
+    }
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
+        self.weight = weight;
+        self
+    }
+
+    pub fn alter_id(&mut self, id: &str) -> &mut Self {
+        self.id.with_value(id);
+        self
+    }
+
+    pub fn alter_classes(&mut self, classes: &str, op: ClassesOp) -> &mut Self {
+        self.classes.alter(classes, op);
+        self
+    }
+
+    pub fn alter_template(&mut self, template: &str) -> &mut Self {
         self.template = template.to_owned();
         self
     }
@@ -98,15 +115,11 @@ impl Row {
         self.id.option()
     }
 
-    pub fn classes(&self, default: &str) -> Option<String> {
-        self.classes.option(default)
+    pub fn classes(&self) -> &Option<String> {
+        self.classes.option()
     }
 
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
 }
-
-fn always() -> bool {
-    true
-}
diff --git a/pagetop/src/base/component/image.rs b/pagetop/src/base/component/image.rs
index 1384f4df..62690679 100644
--- a/pagetop/src/base/component/image.rs
+++ b/pagetop/src/base/component/image.rs
@@ -12,11 +12,11 @@ pub struct Image {
 impl PageComponent for Image {
     fn new() -> Self {
         Image {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
-            source    : OptAttr::none(),
-            id        : OptIden::none(),
-            classes   : Classes::none(),
+            source    : OptAttr::new(),
+            id        : OptIden::new(),
+            classes   : Classes::new_with_default("img-fluid"),
             template  : "default".to_owned(),
         }
     }
@@ -34,7 +34,7 @@ impl PageComponent for Image {
             img
                 src=[self.source()]
                 id=[self.id()]
-                class=[self.classes("img-fluid")];
+                class=[self.classes()];
         }
     }
 }
@@ -47,36 +47,63 @@ impl Image {
     // Image BUILDER.
 
     pub fn with_renderable(mut self, renderable: fn() -> bool) -> Self {
-        self.renderable = renderable;
+        self.alter_renderable(renderable);
         self
     }
 
     pub fn with_weight(mut self, weight: i8) -> Self {
-        self.weight = weight;
+        self.alter_weight(weight);
         self
     }
 
     pub fn with_source(mut self, source: &str) -> Self {
-        self.source.with_value(source);
+        self.alter_source(source);
         self
     }
 
     pub fn with_id(mut self, id: &str) -> Self {
-        self.id.with_value(id);
+        self.alter_id(id);
         self
     }
 
-    pub fn set_classes(mut self, classes: &str) -> Self {
-        self.classes.set_classes(classes);
-        self
-    }
-
-    pub fn add_classes(mut self, classes: &str) -> Self {
-        self.classes.add_classes(classes);
+    pub fn with_classes(mut self, classes: &str, op: ClassesOp) -> Self {
+        self.alter_classes(classes, op);
         self
     }
 
     pub fn using_template(mut self, template: &str) -> Self {
+        self.alter_template(template);
+        self
+    }
+
+    // Image ALTER.
+
+    pub fn alter_renderable(&mut self, renderable: fn() -> bool) -> &mut Self {
+        self.renderable = renderable;
+        self
+    }
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
+        self.weight = weight;
+        self
+    }
+
+    pub fn alter_source(&mut self, source: &str) -> &mut Self {
+        self.source.with_value(source);
+        self
+    }
+
+    pub fn alter_id(&mut self, id: &str) -> &mut Self {
+        self.id.with_value(id);
+        self
+    }
+
+    pub fn alter_classes(&mut self, classes: &str, op: ClassesOp) -> &mut Self {
+        self.classes.alter(classes, op);
+        self
+    }
+
+    pub fn alter_template(&mut self, template: &str) -> &mut Self {
         self.template = template.to_owned();
         self
     }
@@ -91,15 +118,11 @@ impl Image {
         self.id.option()
     }
 
-    pub fn classes(&self, default: &str) -> Option<String> {
-        self.classes.option(default)
+    pub fn classes(&self) -> &Option<String> {
+        self.classes.option()
     }
 
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
 }
-
-fn always() -> bool {
-    true
-}
diff --git a/pagetop/src/base/component/menu.rs b/pagetop/src/base/component/menu.rs
index 01a60129..68c5c97e 100644
--- a/pagetop/src/base/component/menu.rs
+++ b/pagetop/src/base/component/menu.rs
@@ -23,7 +23,7 @@ pub struct MenuItem {
 impl PageComponent for MenuItem {
     fn new() -> Self {
         MenuItem {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             item_type : MenuItemType::Void,
         }
@@ -72,7 +72,7 @@ impl PageComponent for MenuItem {
 impl MenuItem {
     pub fn label(label: &str) -> Self {
         MenuItem {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             item_type : MenuItemType::Label(label.to_owned()),
         }
@@ -80,7 +80,7 @@ impl MenuItem {
 
     pub fn link(label: &str, path: &str) -> Self {
         MenuItem {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             item_type : MenuItemType::Link(
                 label.to_owned(),
@@ -91,7 +91,7 @@ impl MenuItem {
 
     pub fn link_blank(label: &str, path: &str) -> Self {
         MenuItem {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             item_type : MenuItemType::LinkBlank(
                 label.to_owned(),
@@ -102,7 +102,7 @@ impl MenuItem {
 
     pub fn html(html: Markup) -> Self {
         MenuItem {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             item_type : MenuItemType::Html(html),
         }
@@ -110,7 +110,7 @@ impl MenuItem {
 
     pub fn separator() -> Self {
         MenuItem {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             item_type : MenuItemType::Separator,
         }
@@ -118,7 +118,7 @@ impl MenuItem {
 
     pub fn submenu(label: &str, menu: Menu) -> Self {
         MenuItem {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             item_type : MenuItemType::Submenu(
                 label.to_owned(),
@@ -130,11 +130,23 @@ impl MenuItem {
     // MenuItem BUILDER.
 
     pub fn with_renderable(mut self, renderable: fn() -> bool) -> Self {
-        self.renderable = renderable;
+        self.alter_renderable(renderable);
         self
     }
 
     pub fn with_weight(mut self, weight: i8) -> Self {
+        self.alter_weight(weight);
+        self
+    }
+
+    // MenuItem ALTER.
+
+    pub fn alter_renderable(&mut self, renderable: fn() -> bool) -> &mut Self {
+        self.renderable = renderable;
+        self
+    }
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
         self.weight = weight;
         self
     }
@@ -162,11 +174,11 @@ pub struct Menu {
 impl PageComponent for Menu {
     fn new() -> Self {
         Menu {
-            renderable: always,
+            renderable: render_always,
             weight    : 0,
             items     : PageContainer::new(),
-            id        : OptIden::none(),
-            classes   : Classes::none(),
+            id        : OptIden::new(),
+            classes   : Classes::new_with_default("sm sm-clean"),
             template  : "default".to_owned(),
         }
     }
@@ -194,7 +206,7 @@ impl PageComponent for Menu {
 
         let id = assets.serial_id(self.name(), self.id());
         html! {
-            ul id=(id) class=[self.classes("sm sm-clean")] {
+            ul id=(id) class=[self.classes()] {
                 (self.items().render(assets))
             }
             script type="text/javascript" defer {
@@ -223,31 +235,53 @@ impl Menu {
     // Menu BUILDER.
 
     pub fn with_renderable(mut self, renderable: fn() -> bool) -> Self {
-        self.renderable = renderable;
+        self.alter_renderable(renderable);
         self
     }
 
     pub fn with_weight(mut self, weight: i8) -> Self {
-        self.weight = weight;
+        self.alter_weight(weight);
         self
     }
 
     pub fn with_id(mut self, id: &str) -> Self {
-        self.id.with_value(id);
+        self.alter_id(id);
         self
     }
 
-    pub fn set_classes(mut self, classes: &str) -> Self {
-        self.classes.set_classes(classes);
-        self
-    }
-
-    pub fn add_classes(mut self, classes: &str) -> Self {
-        self.classes.add_classes(classes);
+    pub fn with_classes(mut self, classes: &str, op: ClassesOp) -> Self {
+        self.alter_classes(classes, op);
         self
     }
 
     pub fn using_template(mut self, template: &str) -> Self {
+        self.alter_template(template);
+        self
+    }
+
+    // Menu ALTER.
+
+    pub fn alter_renderable(&mut self, renderable: fn() -> bool) -> &mut Self {
+        self.renderable = renderable;
+        self
+    }
+
+    pub fn alter_weight(&mut self, weight: i8) -> &mut Self {
+        self.weight = weight;
+        self
+    }
+
+    pub fn alter_id(&mut self, id: &str) -> &mut Self {
+        self.id.with_value(id);
+        self
+    }
+
+    pub fn alter_classes(&mut self, classes: &str, op: ClassesOp) -> &mut Self {
+        self.classes.alter(classes, op);
+        self
+    }
+
+    pub fn alter_template(&mut self, template: &str) -> &mut Self {
         self.template = template.to_owned();
         self
     }
@@ -258,15 +292,11 @@ impl Menu {
         self.id.option()
     }
 
-    pub fn classes(&self, default: &str) -> Option<String> {
-        self.classes.option(default)
+    pub fn classes(&self) -> &Option<String> {
+        self.classes.option()
     }
 
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
 }
-
-fn always() -> bool {
-    true
-}
diff --git a/pagetop/src/base/theme/bulmix/mod.rs b/pagetop/src/base/theme/bulmix/mod.rs
index cf83a8f6..c7aa3cb2 100644
--- a/pagetop/src/base/theme/bulmix/mod.rs
+++ b/pagetop/src/base/theme/bulmix/mod.rs
@@ -32,33 +32,21 @@ impl ThemeTrait for BulmixTheme {
             .add_jquery();
     }
 
-    fn render_component(
+    fn before_render_component(
         &self,
         component: &mut dyn PageComponent,
-        assets: &mut PageAssets
-    ) -> Option<Markup> {
+        _assets: &mut PageAssets
+    ) {
         match component.name() {
             "GridRow" => {
                 let row = component.downcast_mut::<grid::Row>().unwrap();
-                row.set_classes_ref("Prueba");
-                None
-                /*
-                Some(html! {
-                    div id=[row.id()] class=[row.classes("columns")] {
-                        (row.columns().render(assets))
-                    }
-                })
-                */
+                row.alter_classes("columns", ClassesOp::SetDefault);
             },
             "GridColumn" => {
-                let col = component.downcast_ref::<grid::Column>().unwrap();
-                Some(html! {
-                    div id=[col.id()] class=[col.classes("column")] {
-                        (col.components().render(assets))
-                    }
-                })
+                let col = component.downcast_mut::<grid::Column>().unwrap();
+                col.alter_classes("column", ClassesOp::SetDefault);
             },
-            _ => None
+            _ => {},
         }
     }
 }
diff --git a/pagetop/src/html/classes.rs b/pagetop/src/html/classes.rs
index 6c41aafb..225d6537 100644
--- a/pagetop/src/html/classes.rs
+++ b/pagetop/src/html/classes.rs
@@ -1,23 +1,82 @@
 use crate::concat_string;
 
-pub struct Classes(String);
+pub enum ClassesOp {
+    Add,
+    AddAfter(&'static str),
+    AddBefore(&'static str),
+    AddFirst,
+    Replace(&'static str),
+    Reset,
+    SetDefault,
+}
+
+pub struct Classes {
+    default: String,
+    added  : String,
+    option : Option<String>,
+}
 
 impl Classes {
-    pub fn none() -> Self {
-        Classes("".to_owned())
+    pub fn new() -> Self {
+        Classes {
+            default: "".to_owned(),
+            added  : "".to_owned(),
+            option : None,
+        }
     }
 
-    pub fn set_classes(&mut self, classes: &str) -> &mut Self {
-        self.0 = classes.to_owned();
+    pub fn new_with_default(default: &str) -> Self {
+        let mut classes = Self::new();
+        classes.alter(default, ClassesOp::SetDefault);
+        classes
+    }
+
+    pub fn alter(&mut self, classes: &str, op: ClassesOp) -> &Self {
+        let classes = classes.trim();
+        match op {
+            ClassesOp::Add => self.added.push_str(concat_string!(" ", classes).as_str()),
+
+            ClassesOp::AddAfter(class) => {
+                let mut v_added: Vec<&str> = self.added.split_ascii_whitespace().collect();
+                match v_added.iter().position(|c| c.eq(&class)) {
+                    Some(pos) => v_added.insert(pos + 1, classes),
+                    _ => v_added.push(classes),
+                }
+                self.added = v_added.join(" ");
+            },
+
+            ClassesOp::AddBefore(class) => {
+                let mut v_added: Vec<&str> = self.added.split_ascii_whitespace().collect();
+                match v_added.iter().position(|c| c.eq(&class)) {
+                    Some(pos) => v_added.insert(pos, classes),
+                    _ => v_added.insert(0, classes),
+                }
+                self.added = v_added.join(" ");
+            },
+
+            ClassesOp::AddFirst => self.added = concat_string!(classes, " ", self.added),
+
+            ClassesOp::Replace(class) => {
+                let mut v_added: Vec<&str> = self.added.split_ascii_whitespace().collect();
+                match v_added.iter().position(|c| c.eq(&class)) {
+                    Some(pos) => {
+                        v_added.remove(pos);
+                        v_added.insert(pos, classes);
+                    },
+                    _ => v_added.push(classes),
+                }
+                self.added = v_added.join(" ");
+            },
+
+            ClassesOp::Reset => self.added = classes.to_owned(),
+
+            ClassesOp::SetDefault => self.default = classes.to_owned(),
+        }
+        self.option = Some(concat_string!(self.default, " ", self.added).trim().to_owned());
         self
     }
 
-    pub fn add_classes(&mut self, classes: &str) -> &mut Self {
-        self.0 = concat_string!(self.0, " ", classes).trim().to_owned();
-        self
-    }
-
-    pub fn option(&self, default: &str) -> Option<String> {
-        Some(concat_string!(default.to_owned(), " ", self.0).trim().to_owned())
+    pub fn option(&self) -> &Option<String> {
+        &self.option
     }
 }
diff --git a/pagetop/src/html/mod.rs b/pagetop/src/html/mod.rs
index 52f735fe..56e5c6d2 100644
--- a/pagetop/src/html/mod.rs
+++ b/pagetop/src/html/mod.rs
@@ -5,4 +5,4 @@ pub use optiden::OptIden;
 mod optattr;
 pub use optattr::OptAttr;
 mod classes;
-pub use classes::Classes;
+pub use classes::{Classes, ClassesOp};
diff --git a/pagetop/src/html/optattr.rs b/pagetop/src/html/optattr.rs
index d009e32e..86c21e8c 100644
--- a/pagetop/src/html/optattr.rs
+++ b/pagetop/src/html/optattr.rs
@@ -1,14 +1,14 @@
 pub struct OptAttr(Option<String>);
 
 impl OptAttr {
-    pub fn none() -> Self {
+    pub fn new() -> Self {
         OptAttr(None)
     }
 
-    pub fn some(value: &str) -> Self {
-        let mut o = OptAttr(None);
-        o.with_value(value);
-        o
+    pub fn new_with_value(value: &str) -> Self {
+        let mut option = Self::new();
+        option.with_value(value);
+        option
     }
 
     pub fn with_value(&mut self, value: &str) -> &mut Self {
diff --git a/pagetop/src/html/optiden.rs b/pagetop/src/html/optiden.rs
index 52a65c10..450867d9 100644
--- a/pagetop/src/html/optiden.rs
+++ b/pagetop/src/html/optiden.rs
@@ -1,17 +1,17 @@
 pub struct OptIden(Option<String>);
 
 impl OptIden {
-    pub fn none() -> Self {
+    pub fn new() -> Self {
         OptIden(None)
     }
 
-    pub fn some(id: &str) -> Self {
-        let mut o = OptIden(None);
-        o.with_value(id);
-        o
+    pub fn new_with_value(id: &str) -> Self {
+        let mut option = Self::new();
+        option.with_value(id);
+        option
     }
 
-    pub fn with_value(&mut self, id: &str) -> &mut Self {
+    pub fn with_value(&mut self, id: &str) -> &Self {
         let id = id.trim();
         self.0 = match id.is_empty() {
             true => None,
diff --git a/pagetop/src/response/page/assets.rs b/pagetop/src/response/page/assets.rs
index 3d42a06f..8ab4d2eb 100644
--- a/pagetop/src/response/page/assets.rs
+++ b/pagetop/src/response/page/assets.rs
@@ -257,7 +257,7 @@ impl PageAssets {
 
     /// Assets GETTERS.
 
-    pub fn theme(&mut self) -> &'static dyn ThemeTrait {
+    pub(crate) fn theme(&mut self) -> &'static dyn ThemeTrait {
         self.theme
     }
 
diff --git a/pagetop/src/response/page/component.rs b/pagetop/src/response/page/component.rs
index 630b8a9b..05528fc8 100644
--- a/pagetop/src/response/page/component.rs
+++ b/pagetop/src/response/page/component.rs
@@ -33,6 +33,10 @@ pub trait PageComponent: Downcast + Send + Sync {
         0
     }
 
+    #[allow(unused_variables)]
+    fn before_render(&mut self, assets: &mut PageAssets) {
+    }
+
     #[allow(unused_variables)]
     fn default_render(&self, assets: &mut PageAssets) -> Markup {
         html! {}
diff --git a/pagetop/src/response/page/mod.rs b/pagetop/src/response/page/mod.rs
index f34070e2..527f74f9 100644
--- a/pagetop/src/response/page/mod.rs
+++ b/pagetop/src/response/page/mod.rs
@@ -17,3 +17,6 @@ pub use page::Page;
 pub use page::render_component;
 pub use page::add_component_to;
 
+pub fn render_always() -> bool { true }
+
+pub fn render_never() -> bool { false }
\ No newline at end of file
diff --git a/pagetop/src/response/page/page.rs b/pagetop/src/response/page/page.rs
index 56db5ecc..f7bee609 100644
--- a/pagetop/src/response/page/page.rs
+++ b/pagetop/src/response/page/page.rs
@@ -1,6 +1,6 @@
 use crate::{Lazy, app, trace};
 use crate::config::SETTINGS;
-use crate::html::{Classes, DOCTYPE, Markup, OptAttr, html};
+use crate::html::*;
 use crate::response::page::*;
 
 use std::sync::RwLock;
@@ -55,18 +55,18 @@ impl<'a> Page<'a> {
     pub fn new() -> Self {
         Page {
             language    : match &*DEFAULT_LANGUAGE {
-                Some(language) => OptAttr::some(language),
-                _ => OptAttr::none(),
+                Some(language) => OptAttr::new_with_value(language),
+                _ => OptAttr::new(),
             },
             direction   : match &*DEFAULT_DIRECTION {
-                Some(direction) => OptAttr::some(direction),
-                _ => OptAttr::none(),
+                Some(direction) => OptAttr::new_with_value(direction),
+                _ => OptAttr::new(),
             },
-            title       : OptAttr::none(),
-            description : OptAttr::none(),
+            title       : OptAttr::new(),
+            description : OptAttr::new(),
             assets      : PageAssets::new(),
             regions     : COMPONENTS.read().unwrap().clone(),
-            body_classes: Classes::none(),
+            body_classes: Classes::new_with_default("body"),
             template    : "default".to_owned(),
         }
     }
@@ -110,13 +110,8 @@ impl<'a> Page<'a> {
         self
     }
 
-    pub fn set_body_classes(&mut self, classes: &str) -> &mut Self {
-        self.body_classes.set_classes(classes);
-        self
-    }
-
-    pub fn add_body_classes(&mut self, classes: &str) -> &mut Self {
-        self.body_classes.add_classes(classes);
+    pub fn alter_body_classes(&mut self, classes: &str, op: ClassesOp) -> &mut Self {
+        self.body_classes.alter(classes, op);
         self
     }
 
@@ -147,8 +142,8 @@ impl<'a> Page<'a> {
         &mut self.assets
     }
 
-    pub fn body_classes(&self, default: &str) -> Option<String> {
-        self.body_classes.option(default)
+    pub fn body_classes(&self) -> &Option<String> {
+        self.body_classes.option()
     }
 
     pub fn template(&self) -> &str {
@@ -192,14 +187,15 @@ impl<'a> Page<'a> {
     }
 }
 
-pub fn render_component(
-    component: &mut dyn PageComponent,
-    assets: &mut PageAssets
-) -> Markup {
+pub fn render_component(component: &mut dyn PageComponent, assets: &mut PageAssets) -> Markup {
+    component.before_render(assets);
+    assets.theme().before_render_component(component, assets);
     match component.is_renderable() {
-        true => match assets.theme().render_component(component, assets) {
-            Some(html) => html,
-            None => component.default_render(assets)
+        true => {
+            match assets.theme().render_component(component, assets) {
+                Some(html) => html,
+                None => component.default_render(assets)
+            }
         },
         false => html! {}
     }
diff --git a/pagetop/src/theme/definition.rs b/pagetop/src/theme/definition.rs
index 457860c7..983bf0a6 100644
--- a/pagetop/src/theme/definition.rs
+++ b/pagetop/src/theme/definition.rs
@@ -55,7 +55,7 @@ pub trait ThemeTrait: Send + Sync {
 
     fn render_page_body(&self, page: &mut Page) -> Markup {
         html! {
-            body class=[page.body_classes("body")] {
+            body class=[page.body_classes()] {
                 @match page.template() {
                     "admin" => {
                         @for region in &["top-menu", "side-menu", "content"] {
@@ -75,10 +75,29 @@ pub trait ThemeTrait: Send + Sync {
     }
 
     #[allow(unused_variables)]
-    fn render_component(
+    fn before_render_component(
         &self,
         component: &mut dyn PageComponent,
         assets: &mut PageAssets
+    ) {
+    /*
+        Cómo usarlo:
+
+        match component.name() {
+            "Block" => {
+                let block = component.downcast_mut::<Block>().unwrap();
+                block.alter_title("New title");
+            },
+            _ => {},
+        }
+    */
+    }
+
+    #[allow(unused_variables)]
+    fn render_component(
+        &self,
+        component: &dyn PageComponent,
+        assets: &mut PageAssets
     ) -> Option<Markup> {
         None
     /*
@@ -89,10 +108,10 @@ pub trait ThemeTrait: Send + Sync {
                 let block = component.downcast_ref::<Block>().unwrap();
                 match block.template() {
                     "default" => Some(block_default(block)),
-                    _ => None
+                    _ => None,
                 }
             },
-            _ => None
+            _ => None,
         }
     */
     }