diff --git a/pagetop/Cargo.toml b/pagetop/Cargo.toml
index 01eb60ec..8598de96 100644
--- a/pagetop/Cargo.toml
+++ b/pagetop/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "pagetop"
-version = "0.0.5"
+version = "0.0.6"
 edition = "2021"
 
 authors = [
diff --git a/pagetop/src/base/component/block.rs b/pagetop/src/base/component/block.rs
index 976c27bc..fdf9922d 100644
--- a/pagetop/src/base/component/block.rs
+++ b/pagetop/src/base/component/block.rs
@@ -3,9 +3,10 @@ use crate::prelude::*;
 pub struct Block {
     renderable: fn() -> bool,
     weight    : i8,
-    id        : OptIden,
     title     : OptAttr,
     html      : Vec<Markup>,
+    id        : OptIden,
+    classes   : Classes,
     template  : String,
 }
 
@@ -15,9 +16,10 @@ impl PageComponent for Block {
         Block {
             renderable: always,
             weight    : 0,
-            id        : OptIden::none(),
             title     : OptAttr::none(),
             html      : Vec::new(),
+            id        : OptIden::none(),
+            classes   : Classes::none(),
             template  : "default".to_owned(),
         }
     }
@@ -33,7 +35,7 @@ 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="block" {
+            div id=(id) class=[self.classes("block")] {
                 @match self.title() {
                     Some(title) => h2 class="block-title" { (title) },
                     None => {}
@@ -66,11 +68,6 @@ impl Block {
         self
     }
 
-    pub fn with_id(mut self, id: &str) -> Self {
-        self.id.with_value(id);
-        self
-    }
-
     pub fn with_title(mut self, title: &str) -> Self {
         self.title.with_value(title);
         self
@@ -81,6 +78,21 @@ impl Block {
         self
     }
 
+    pub fn with_id(mut self, id: &str) -> Self {
+        self.id.with_value(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);
+        self
+    }
+
     pub fn using_template(mut self, template: &str) -> Self {
         self.template = template.to_owned();
         self
@@ -88,10 +100,6 @@ impl Block {
 
     // Block GETTERS.
 
-    pub fn id(&self) -> &Option<String> {
-        self.id.option()
-    }
-
     pub fn title(&self) -> &Option<String> {
         self.title.option()
     }
@@ -100,6 +108,14 @@ impl Block {
         &self.html
     }
 
+    pub fn id(&self) -> &Option<String> {
+        self.id.option()
+    }
+
+    pub fn classes(&self, default: &str) -> Option<String> {
+        self.classes.option(default)
+    }
+
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
diff --git a/pagetop/src/base/component/container.rs b/pagetop/src/base/component/container.rs
index cba905d6..94003ae0 100644
--- a/pagetop/src/base/component/container.rs
+++ b/pagetop/src/base/component/container.rs
@@ -6,8 +6,9 @@ pub struct Container {
     renderable: fn() -> bool,
     weight    : i8,
     container : ContainerType,
-    id        : OptIden,
     components: PageContainer,
+    id        : OptIden,
+    classes   : Classes,
     template  : String,
 }
 
@@ -18,8 +19,9 @@ impl PageComponent for Container {
             renderable: always,
             weight    : 0,
             container : ContainerType::Wrapper,
-            id        : OptIden::none(),
             components: PageContainer::new(),
+            id        : OptIden::none(),
+            classes   : Classes::none(),
             template  : "default".to_owned(),
         }
     }
@@ -35,35 +37,35 @@ impl PageComponent for Container {
     fn default_render(&self, assets: &mut PageAssets) -> Markup {
         match self.container_type() {
             ContainerType::Header => html! {
-                header id=[self.id()] class="header" {
+                header id=[self.id()] class=[self.classes("header")] {
                     div class="container" {
                         (self.render_components(assets))
                     }
                 }
             },
             ContainerType::Footer => html! {
-                footer id=[self.id()] class="footer" {
+                footer id=[self.id()] class=[self.classes("footer")] {
                     div class="container" {
                         (self.render_components(assets))
                     }
                 }
             },
             ContainerType::Main => html! {
-                main id=[self.id()] class="main" {
+                main id=[self.id()] class=[self.classes("main")] {
                     div class="container" {
                         (self.render_components(assets))
                     }
                 }
             },
             ContainerType::Section => html! {
-                section id=[self.id()] class="section" {
+                section id=[self.id()] class=[self.classes("section")] {
                     div class="container" {
                         (self.render_components(assets))
                     }
                 }
             },
             _ => html! {
-                div id=[self.id()] class="container" {
+                div id=[self.id()] class=[self.classes("container")] {
                     (self.render_components(assets))
                 }
             }
@@ -109,13 +111,23 @@ impl Container {
         self
     }
 
+    pub fn add(mut self, component: impl PageComponent) -> Self {
+        self.components.add(component);
+        self
+    }
+
     pub fn with_id(mut self, id: &str) -> Self {
         self.id.with_value(id);
         self
     }
 
-    pub fn add(mut self, component: impl PageComponent) -> Self {
-        self.components.add(component);
+    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);
         self
     }
 
@@ -134,6 +146,10 @@ impl Container {
         self.id.option()
     }
 
+    pub fn classes(&self, default: &str) -> Option<String> {
+        self.classes.option(default)
+    }
+
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
diff --git a/pagetop/src/base/component/form/button.rs b/pagetop/src/base/component/form/button.rs
index fbe25738..b2f59609 100644
--- a/pagetop/src/base/component/form/button.rs
+++ b/pagetop/src/base/component/form/button.rs
@@ -10,6 +10,7 @@ pub struct Button {
     value      : OptAttr,
     autofocus  : OptAttr,
     disabled   : OptAttr,
+    classes    : Classes,
     template   : String,
 }
 
@@ -24,6 +25,7 @@ impl PageComponent for Button {
             value      : OptAttr::none(),
             autofocus  : OptAttr::none(),
             disabled   : OptAttr::none(),
+            classes    : Classes::none(),
             template   : "default".to_owned(),
         }
     }
@@ -50,7 +52,7 @@ impl PageComponent for Button {
             button
                 type=(button_type)
                 id=[id]
-                class=(button_class)
+                class=[self.classes(button_class)]
                 name=[self.name()]
                 value=[self.value()]
                 autofocus=[self.autofocus()]
@@ -121,6 +123,16 @@ impl Button {
         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);
+        self
+    }
+
     pub fn using_template(mut self, template: &str) -> Self {
         self.template = template.to_owned();
         self
@@ -148,6 +160,10 @@ impl Button {
         self.disabled.option()
     }
 
+    pub fn classes(&self, default: &str) -> Option<String> {
+        self.classes.option(default)
+    }
+
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
diff --git a/pagetop/src/base/component/form/date.rs b/pagetop/src/base/component/form/date.rs
index 906f5bbc..f1270a82 100644
--- a/pagetop/src/base/component/form/date.rs
+++ b/pagetop/src/base/component/form/date.rs
@@ -13,6 +13,7 @@ pub struct Date {
     readonly    : OptAttr,
     required    : OptAttr,
     help_text   : OptAttr,
+    classes     : Classes,
     template    : String,
 }
 
@@ -32,6 +33,7 @@ impl PageComponent for Date {
             readonly    : OptAttr::none(),
             required    : OptAttr::none(),
             help_text   : OptAttr::none(),
+            classes     : Classes::none(),
             template    : "default".to_owned(),
         }
     }
@@ -45,7 +47,7 @@ impl PageComponent for Date {
     }
 
     fn default_render(&self, _: &mut PageAssets) -> Markup {
-        let (class, id) = match self.name() {
+        let (classes, id) = match self.name() {
             Some(name) => (
                 concat_string!("form-item form-item-", name, " form-type-date"),
                 Some(concat_string!("edit-", name))
@@ -56,7 +58,7 @@ impl PageComponent for Date {
             )
         };
         html! {
-            div class=(class) {
+            div class=[self.classes(classes.as_str())] {
                 @match self.label() {
                     Some(label) => label class="form-label" for=[&id] {
                         (label) " "
@@ -169,6 +171,16 @@ impl Date {
         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);
+        self
+    }
+
     pub fn using_template(mut self, template: &str) -> Self {
         self.template = template.to_owned();
         self
@@ -216,6 +228,10 @@ impl Date {
         self.help_text.option()
     }
 
+    pub fn classes(&self, default: &str) -> Option<String> {
+        self.classes.option(default)
+    }
+
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
diff --git a/pagetop/src/base/component/form/form.rs b/pagetop/src/base/component/form/form.rs
index 5ecea5e0..c4d8e206 100644
--- a/pagetop/src/base/component/form/form.rs
+++ b/pagetop/src/base/component/form/form.rs
@@ -5,11 +5,12 @@ pub enum FormMethod {Get, Post}
 pub struct Form {
     renderable: fn() -> bool,
     weight    : i8,
-    id        : OptIden,
     action    : OptAttr,
     charset   : OptAttr,
     method    : FormMethod,
     elements  : PageContainer,
+    id        : OptIden,
+    classes   : Classes,
     template  : String,
 }
 
@@ -19,11 +20,12 @@ impl PageComponent for Form {
         Form {
             renderable: always,
             weight    : 0,
-            id        : OptIden::none(),
             action    : OptAttr::none(),
             charset   : OptAttr::some("UTF-8"),
             method    : FormMethod::Post,
             elements  : PageContainer::new(),
+            id        : OptIden::none(),
+            classes   : Classes::none(),
             template  : "default".to_owned(),
         }
     }
@@ -44,6 +46,7 @@ impl PageComponent for Form {
         html! {
             form
                 id=[self.id()]
+                class=[self.classes("form")]
                 action=[self.action()]
                 method=[method]
                 accept-charset=[self.charset()]
@@ -70,11 +73,6 @@ impl Form {
         self
     }
 
-    pub fn with_id(mut self, id: &str) -> Self {
-        self.id.with_value(id);
-        self
-    }
-
     pub fn with_action(mut self, action: &str) -> Self {
         self.action.with_value(action);
         self
@@ -95,6 +93,21 @@ impl Form {
         self
     }
 
+    pub fn with_id(mut self, id: &str) -> Self {
+        self.id.with_value(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);
+        self
+    }
+
     pub fn using_template(mut self, template: &str) -> Self {
         self.template = template.to_owned();
         self
@@ -102,10 +115,6 @@ impl Form {
 
     // Form GETTERS.
 
-    pub fn id(&self) -> &Option<String> {
-        self.id.option()
-    }
-
     pub fn action(&self) -> &Option<String> {
         self.action.option()
     }
@@ -118,6 +127,14 @@ impl Form {
         &self.method
     }
 
+    pub fn id(&self) -> &Option<String> {
+        self.id.option()
+    }
+
+    pub fn classes(&self, default: &str) -> Option<String> {
+        self.classes.option(default)
+    }
+
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
diff --git a/pagetop/src/base/component/form/input.rs b/pagetop/src/base/component/form/input.rs
index 7dded20f..2e1af61d 100644
--- a/pagetop/src/base/component/form/input.rs
+++ b/pagetop/src/base/component/form/input.rs
@@ -19,6 +19,7 @@ pub struct Input {
     readonly    : OptAttr,
     required    : OptAttr,
     help_text   : OptAttr,
+    classes     : Classes,
     template    : String,
 }
 
@@ -42,6 +43,7 @@ impl PageComponent for Input {
             readonly    : OptAttr::none(),
             required    : OptAttr::none(),
             help_text   : OptAttr::none(),
+            classes     : Classes::none(),
             template    : "default".to_owned(),
         }
     }
@@ -239,6 +241,16 @@ impl Input {
         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);
+        self
+    }
+
     pub fn using_template(mut self, template: &str) -> Self {
         self.template = template.to_owned();
         self
@@ -302,6 +314,10 @@ impl Input {
         self.help_text.option()
     }
 
+    pub fn classes(&self, default: &str) -> Option<String> {
+        self.classes.option(default)
+    }
+
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
diff --git a/pagetop/src/base/component/grid/column.rs b/pagetop/src/base/component/grid/column.rs
index 6d3a7b19..f5bc4669 100644
--- a/pagetop/src/base/component/grid/column.rs
+++ b/pagetop/src/base/component/grid/column.rs
@@ -3,9 +3,9 @@ use crate::prelude::*;
 pub struct Column {
     renderable: fn() -> bool,
     weight    : i8,
+    components: PageContainer,
     id        : OptIden,
     classes   : Classes,
-    components: PageContainer,
     template  : String,
 }
 
@@ -15,13 +15,17 @@ impl PageComponent for Column {
         Column {
             renderable: always,
             weight    : 0,
-            id        : OptIden::none(),
-            classes   : Classes::some(vec!["col"]),
             components: PageContainer::new(),
+            id        : OptIden::none(),
+            classes   : Classes::none(),
             template  : "default".to_owned(),
         }
     }
 
+    fn name(&self) -> &'static str {
+        "GridColumn"
+    }
+
     fn is_renderable(&self) -> bool {
         (self.renderable)()
     }
@@ -32,7 +36,7 @@ impl PageComponent for Column {
 
     fn default_render(&self, assets: &mut PageAssets) -> Markup {
         html! {
-            div id=[self.id()] class=[self.classes()] {
+            div id=[self.id()] class=[self.classes("col")] {
                 (self.render_components(assets))
             }
         }
@@ -53,18 +57,23 @@ impl Column {
         self
     }
 
+    pub fn add(mut self, component: impl PageComponent) -> Self {
+        self.components.add(component);
+        self
+    }
+
     pub fn with_id(mut self, id: &str) -> Self {
         self.id.with_value(id);
         self
     }
 
-    pub fn add_classes(mut self, classes: Vec<&str>) -> Self {
-        self.classes.add_classes(classes);
+    pub fn set_classes(mut self, classes: &str) -> Self {
+        self.classes.set_classes(classes);
         self
     }
 
-    pub fn add(mut self, component: impl PageComponent) -> Self {
-        self.components.add(component);
+    pub fn add_classes(mut self, classes: &str) -> Self {
+        self.classes.add_classes(classes);
         self
     }
 
@@ -79,8 +88,8 @@ impl Column {
         self.id.option()
     }
 
-    pub fn classes(&self) -> &Option<String> {
-        self.classes.option()
+    pub fn classes(&self, default: &str) -> Option<String> {
+        self.classes.option(default)
     }
 
     pub fn template(&self) -> &str {
diff --git a/pagetop/src/base/component/grid/row.rs b/pagetop/src/base/component/grid/row.rs
index b1bb2c24..8437c1fe 100644
--- a/pagetop/src/base/component/grid/row.rs
+++ b/pagetop/src/base/component/grid/row.rs
@@ -3,9 +3,9 @@ use crate::prelude::*;
 pub struct Row {
     renderable: fn() -> bool,
     weight    : i8,
+    columns   : PageContainer,
     id        : OptIden,
     classes   : Classes,
-    columns   : PageContainer,
     template  : String,
 }
 
@@ -15,13 +15,17 @@ impl PageComponent for Row {
         Row {
             renderable: always,
             weight    : 0,
-            id        : OptIden::none(),
-            classes   : Classes::some(vec!["row"]),
             columns   : PageContainer::new(),
+            id        : OptIden::none(),
+            classes   : Classes::none(),
             template  : "default".to_owned(),
         }
     }
 
+    fn name(&self) -> &'static str {
+        "GridRow"
+    }
+
     fn is_renderable(&self) -> bool {
         (self.renderable)()
     }
@@ -32,7 +36,7 @@ impl PageComponent for Row {
 
     fn default_render(&self, assets: &mut PageAssets) -> Markup {
         html! {
-            div id=[self.id()] class=[self.classes()] {
+            div id=[self.id()] class=[self.classes("row")] {
                 (self.render_columns(assets))
             }
         }
@@ -53,18 +57,23 @@ impl Row {
         self
     }
 
+    pub fn add_column(mut self, column: grid::Column) -> Self {
+        self.columns.add(column);
+        self
+    }
+
     pub fn with_id(mut self, id: &str) -> Self {
         self.id.with_value(id);
         self
     }
 
-    pub fn add_classes(mut self, classes: Vec<&str>) -> Self {
-        self.classes.add_classes(classes);
+    pub fn set_classes(mut self, classes: &str) -> Self {
+        self.classes.set_classes(classes);
         self
     }
 
-    pub fn add_column(mut self, column: grid::Column) -> Self {
-        self.columns.add(column);
+    pub fn add_classes(mut self, classes: &str) -> Self {
+        self.classes.add_classes(classes);
         self
     }
 
@@ -79,8 +88,8 @@ impl Row {
         self.id.option()
     }
 
-    pub fn classes(&self) -> &Option<String> {
-        self.classes.option()
+    pub fn classes(&self, default: &str) -> Option<String> {
+        self.classes.option(default)
     }
 
     pub fn template(&self) -> &str {
diff --git a/pagetop/src/base/component/image.rs b/pagetop/src/base/component/image.rs
index 799aab63..c324782a 100644
--- a/pagetop/src/base/component/image.rs
+++ b/pagetop/src/base/component/image.rs
@@ -4,6 +4,8 @@ pub struct Image {
     renderable: fn() -> bool,
     weight    : i8,
     source    : OptAttr,
+    id        : OptIden,
+    classes   : Classes,
     template  : String,
 }
 
@@ -14,6 +16,8 @@ impl PageComponent for Image {
             renderable: always,
             weight    : 0,
             source    : OptAttr::none(),
+            id        : OptIden::none(),
+            classes   : Classes::none(),
             template  : "default".to_owned(),
         }
     }
@@ -28,7 +32,10 @@ impl PageComponent for Image {
 
     fn default_render(&self, _: &mut PageAssets) -> Markup {
         html! {
-            img src=[self.source()] class="img-fluid";
+            img
+                src=[self.source()]
+                id=[self.id()]
+                class=[self.classes("img-fluid")];
         }
     }
 }
@@ -56,6 +63,21 @@ impl Image {
         self
     }
 
+    pub fn with_id(mut self, id: &str) -> Self {
+        self.id.with_value(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);
+        self
+    }
+
     pub fn using_template(mut self, template: &str) -> Self {
         self.template = template.to_owned();
         self
@@ -67,6 +89,14 @@ impl Image {
         self.source.option()
     }
 
+    pub fn id(&self) -> &Option<String> {
+        self.id.option()
+    }
+
+    pub fn classes(&self, default: &str) -> Option<String> {
+        self.classes.option(default)
+    }
+
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
diff --git a/pagetop/src/base/component/menu.rs b/pagetop/src/base/component/menu.rs
index 253cd3d8..91881908 100644
--- a/pagetop/src/base/component/menu.rs
+++ b/pagetop/src/base/component/menu.rs
@@ -155,8 +155,9 @@ impl MenuItem {
 pub struct Menu {
     renderable: fn() -> bool,
     weight    : i8,
-    id        : OptIden,
     items     : PageContainer,
+    id        : OptIden,
+    classes   : Classes,
     template  : String,
 }
 
@@ -166,8 +167,9 @@ impl PageComponent for Menu {
         Menu {
             renderable: always,
             weight    : 0,
-            id        : OptIden::none(),
             items     : PageContainer::new(),
+            id        : OptIden::none(),
+            classes   : Classes::none(),
             template  : "default".to_owned(),
         }
     }
@@ -195,7 +197,7 @@ impl PageComponent for Menu {
 
         let id = assets.serial_id(self.name(), self.id());
         html! {
-            ul id=(id) class="sm sm-clean" {
+            ul id=(id) class=[self.classes("sm sm-clean")] {
                 (self.render_items(assets))
             }
             script type="text/javascript" defer {
@@ -222,13 +224,23 @@ impl Menu {
         self
     }
 
+    pub fn add(mut self, item: MenuItem) -> Self {
+        self.items.add(item);
+        self
+    }
+
     pub fn with_id(mut self, id: &str) -> Self {
         self.id.with_value(id);
         self
     }
 
-    pub fn add(mut self, item: MenuItem) -> Self {
-        self.items.add(item);
+    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);
         self
     }
 
@@ -243,6 +255,10 @@ impl Menu {
         self.id.option()
     }
 
+    pub fn classes(&self, default: &str) -> Option<String> {
+        self.classes.option(default)
+    }
+
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
diff --git a/pagetop/src/base/theme/bulmix/mod.rs b/pagetop/src/base/theme/bulmix/mod.rs
index b8d57ba7..0e8a4d9b 100644
--- a/pagetop/src/base/theme/bulmix/mod.rs
+++ b/pagetop/src/base/theme/bulmix/mod.rs
@@ -31,4 +31,30 @@ impl ThemeTrait for BulmixTheme {
             )
             .add_jquery();
     }
+
+    fn render_component(
+        &self,
+        component: &dyn PageComponent,
+        assets: &mut PageAssets
+    ) -> Option<Markup> {
+        match component.name() {
+            "GridRow" => {
+                let row = component.downcast_ref::<grid::Row>().unwrap();
+                Some(html! {
+                    div id=[row.id()] class=[row.classes("columns")] {
+                        (row.render_columns(assets))
+                    }
+                })
+            },
+            "GridColumn" => {
+                let col = component.downcast_ref::<grid::Column>().unwrap();
+                Some(html! {
+                    div id=[col.id()] class=[col.classes("column")] {
+                        (col.render_components(assets))
+                    }
+                })
+            },
+            _ => None
+        }
+    }
 }
diff --git a/pagetop/src/html/classes.rs b/pagetop/src/html/classes.rs
index c2a35984..6c41aafb 100644
--- a/pagetop/src/html/classes.rs
+++ b/pagetop/src/html/classes.rs
@@ -1,48 +1,23 @@
 use crate::concat_string;
 
-pub struct Classes(Option<String>);
+pub struct Classes(String);
 
 impl Classes {
     pub fn none() -> Self {
-        Classes(None)
+        Classes("".to_owned())
     }
 
-    pub fn some(classes: Vec<&str>) -> Self {
-        let mut c = Classes::none();
-        c.add_classes(classes);
-        c
+    pub fn set_classes(&mut self, classes: &str) -> &mut Self {
+        self.0 = classes.to_owned();
+        self
     }
 
-    pub fn add_classes(&mut self, classes: Vec<&str>) {
-        for class in classes.iter() {
-            self.add_class(class);
-        }
+    pub fn add_classes(&mut self, classes: &str) -> &mut Self {
+        self.0 = concat_string!(self.0, " ", classes).trim().to_owned();
+        self
     }
 
-    fn add_class(&mut self, class: &str) {
-        let class = class.trim().replace(" ", "_");
-        if !class.is_empty() {
-            match &self.0 {
-                None => self.0 = Some(class),
-                Some(classes) => if !classes.split(" ").any(|c| *c == class) {
-                    self.0 = Some(concat_string!(classes, " ", class))
-                }
-            }
-        }
-    }
-
-    pub fn classes(&self) -> &str {
-        match &self.0 {
-            Some(classes) => classes.as_str(),
-            None => "",
-        }
-    }
-
-    pub fn has_classes(&self) -> bool {
-        self.0 != None
-    }
-
-    pub fn option(&self) -> &Option<String> {
-        &self.0
+    pub fn option(&self, default: &str) -> Option<String> {
+        Some(concat_string!(default.to_owned(), " ", self.0).trim().to_owned())
     }
 }
diff --git a/pagetop/src/html/optattr.rs b/pagetop/src/html/optattr.rs
index a76f33b7..d009e32e 100644
--- a/pagetop/src/html/optattr.rs
+++ b/pagetop/src/html/optattr.rs
@@ -6,17 +6,18 @@ impl OptAttr {
     }
 
     pub fn some(value: &str) -> Self {
-        let mut o = OptAttr::none();
+        let mut o = OptAttr(None);
         o.with_value(value);
         o
     }
 
-    pub fn with_value(&mut self, value: &str) {
+    pub fn with_value(&mut self, value: &str) -> &mut Self {
         let value = value.trim();
         self.0 = match value.is_empty() {
             true => None,
             false => Some(value.to_owned()),
         };
+        self
     }
 
     pub fn option(&self) -> &Option<String> {
diff --git a/pagetop/src/html/optiden.rs b/pagetop/src/html/optiden.rs
index ec46acf1..52a65c10 100644
--- a/pagetop/src/html/optiden.rs
+++ b/pagetop/src/html/optiden.rs
@@ -6,17 +6,18 @@ impl OptIden {
     }
 
     pub fn some(id: &str) -> Self {
-        let mut o = OptIden::none();
+        let mut o = OptIden(None);
         o.with_value(id);
         o
     }
 
-    pub fn with_value(&mut self, id: &str) {
+    pub fn with_value(&mut self, id: &str) -> &mut Self {
         let id = id.trim();
         self.0 = match id.is_empty() {
             true => None,
             false => Some(id.replace(" ", "_")),
         };
+        self
     }
 
     pub fn option(&self) -> &Option<String> {
diff --git a/pagetop/src/response/page/page.rs b/pagetop/src/response/page/page.rs
index 50ff3040..cb561626 100644
--- a/pagetop/src/response/page/page.rs
+++ b/pagetop/src/response/page/page.rs
@@ -45,8 +45,8 @@ pub struct Page<'a> {
     title       : OptAttr,
     description : OptAttr,
     assets      : PageAssets,
-    body_classes: Classes,
     regions     : HashMap<&'a str, PageContainer>,
+    body_classes: Classes,
     template    : String,
 }
 
@@ -64,9 +64,9 @@ impl<'a> Page<'a> {
             },
             title       : OptAttr::none(),
             description : OptAttr::none(),
-            body_classes: Classes::some(vec!["body"]),
             assets      : PageAssets::new(),
             regions     : COMPONENTS.read().unwrap().clone(),
+            body_classes: Classes::none(),
             template    : "default".to_owned(),
         }
     }
@@ -97,11 +97,6 @@ impl<'a> Page<'a> {
         self
     }
 
-    pub fn add_body_classes(&mut self, classes: Vec<&str>) -> &mut Self {
-        self.body_classes.add_classes(classes);
-        self
-    }
-
     pub fn add_to(
         &mut self,
         region: &'a str,
@@ -115,6 +110,16 @@ 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);
+        self
+    }
+
     pub fn using_template(&mut self, template: &str) -> &mut Self {
         self.template = template.to_owned();
         self
@@ -138,14 +143,14 @@ impl<'a> Page<'a> {
         self.description.option()
     }
 
-    pub fn body_classes(&mut self) -> &str {
-        self.body_classes.classes()
-    }
-
     pub fn assets(&mut self) -> &mut PageAssets {
         &mut self.assets
     }
 
+    pub fn body_classes(&self, default: &str) -> Option<String> {
+        self.body_classes.option(default)
+    }
+
     pub fn template(&self) -> &str {
         self.template.as_str()
     }
diff --git a/pagetop/src/theme/definition.rs b/pagetop/src/theme/definition.rs
index 51b1d4c8..acc30f47 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 class=[page.body_classes("body")] {
                 @match page.template() {
                     "admin" => {
                         @for region in &["top-menu", "side-menu", "content"] {
@@ -85,8 +85,8 @@ pub trait ThemeTrait: Send + Sync {
         Cómo usarlo:
 
         match component.name() {
-            "block" => {
-                let block = component.downcast_mut::<Block>().unwrap();
+            "Block" => {
+                let block = component.downcast_ref::<Block>().unwrap();
                 match block.template() {
                     "default" => Some(block_default(block)),
                     _ => None