diff --git a/Cargo.toml b/Cargo.toml
index 168ee872..1b07ae3a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "pagetop"
-version = "0.0.0"
+version = "0.1.0"
 edition = "2021"
 
 authors = [
@@ -24,6 +24,8 @@ categories = [
 ]
 
 [dependencies]
+once_cell = "1.9.0"
+
 actix-web = "4.0.0-rc.3"
 sycamore = { version = "0.8.0-beta.2", features = ["ssr"] }
 
diff --git a/src/core/all.rs b/src/core/all.rs
new file mode 100644
index 00000000..4067a838
--- /dev/null
+++ b/src/core/all.rs
@@ -0,0 +1,7 @@
+use crate::core::{server, state};
+
+pub fn modules(cfg: &mut server::web::ServiceConfig) {
+    for m in state::MODULES.read().unwrap().iter() {
+        m.configure_module(cfg);
+    }
+}
diff --git a/src/core/mod.rs b/src/core/mod.rs
index fc3e282f..3c6040c9 100644
--- a/src/core/mod.rs
+++ b/src/core/mod.rs
@@ -1,3 +1,9 @@
 pub use actix_web::dev::Server;
 
+mod state;
+pub use state::register_module;
+
+mod all;
+
+pub mod module;
 pub mod server;
diff --git a/src/core/module/api.rs b/src/core/module/api.rs
new file mode 100644
index 00000000..37c84786
--- /dev/null
+++ b/src/core/module/api.rs
@@ -0,0 +1,14 @@
+use crate::core::server;
+
+/// Modules must implement this trait.
+pub trait Module: Send + Sync {
+    fn name(&self) -> String;
+
+    fn description(&self) -> String {
+        "".to_string()
+    }
+
+    #[allow(unused_variables)]
+    fn configure_module(&self, cfg: &mut server::web::ServiceConfig) {
+    }
+}
diff --git a/src/core/module/mod.rs b/src/core/module/mod.rs
new file mode 100644
index 00000000..a8f85139
--- /dev/null
+++ b/src/core/module/mod.rs
@@ -0,0 +1,2 @@
+mod api;
+pub use api::Module;
diff --git a/src/core/server/main.rs b/src/core/server/main.rs
index 6a54d243..457bb652 100644
--- a/src/core/server/main.rs
+++ b/src/core/server/main.rs
@@ -1,22 +1,14 @@
-use crate::core::{server, Server};
+use crate::core::{Server, all, server};
 
-async fn greet() -> impl server::Responder {
-    "Hello!"
-}
+pub fn run(bootstrap: Option<fn()>) -> Result<Server, std::io::Error> {
+    // Call application bootstrap.
+    if bootstrap != None {
+        let _ = &(bootstrap.unwrap())();
+    }
 
-async fn greet_with_param(req: server::HttpRequest) -> server::HttpResponse {
-    let name: String = req.match_info().get("name").unwrap_or("World").into();
-    server::HttpResponse::Ok()
-        .body(sycamore::render_to_string(|ctx| sycamore::view! { ctx,
-            p { "Hello " (name) "!" }
-        }))
-}
-
-pub fn run() -> Result<Server, std::io::Error> {
     let server = server::HttpServer::new(|| {
         server::App::new()
-            .route("/", server::web::get().to(greet))
-            .route("/{name}", server::web::get().to(greet_with_param))
+            .configure(&all::modules)
         })
         .bind("127.0.0.1:8000")?
         .run();
diff --git a/src/core/server/mod.rs b/src/core/server/mod.rs
index a1210ce3..d39c1d4d 100644
--- a/src/core/server/mod.rs
+++ b/src/core/server/mod.rs
@@ -1,4 +1,4 @@
-pub use actix_web::{web, App, HttpRequest, HttpResponse, HttpServer, Responder};
+pub use actix_web::{App, HttpRequest, HttpResponse, HttpServer, Responder, web};
 
 mod main;
 pub use main::run;
diff --git a/src/core/state.rs b/src/core/state.rs
new file mode 100644
index 00000000..6ded57b8
--- /dev/null
+++ b/src/core/state.rs
@@ -0,0 +1,16 @@
+use crate::Lazy;
+use crate::core::module::Module;
+
+use std::sync::RwLock;
+
+// -----------------------------------------------------------------------------
+// Registered modules.
+// -----------------------------------------------------------------------------
+
+pub static MODULES: Lazy<RwLock<Vec<&dyn Module>>> = Lazy::new(|| {
+    RwLock::new(vec![])
+});
+
+pub fn register_module(m: &'static (dyn Module + 'static)) {
+    MODULES.write().unwrap().push(m);
+}
diff --git a/src/lib.rs b/src/lib.rs
index 48a67efc..01361a13 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,7 @@
+// Global.
+
+pub use once_cell::sync::Lazy;
+
 pub mod core;
 
 pub use actix_web::main;
diff --git a/src/main.rs b/src/main.rs
index db2a29bc..c1545d0a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,52 @@
-use pagetop::core::server;
+use pagetop::core::module::Module;
+use pagetop::core::{register_module, server};
+
+struct Greet;
+impl Module for Greet {
+    fn name(&self) -> String {
+        "Hello".to_string()
+    }
+
+    fn configure_module(&self, cfg: &mut server::web::ServiceConfig) {
+        cfg.service(
+            server::web::resource("/")
+                .route(server::web::get().to(greet))
+        );
+    }
+}
+
+async fn greet() -> impl server::Responder {
+    "Hello!"
+}
+
+struct GreetWithParam;
+impl Module for GreetWithParam {
+    fn name(&self) -> String {
+        "Hello World!".to_string()
+    }
+
+    fn configure_module(&self, cfg: &mut server::web::ServiceConfig) {
+        cfg.service(
+            server::web::resource("/{name}")
+                .route(server::web::get().to(greet_with_param))
+        );
+    }
+}
+
+async fn greet_with_param(req: server::HttpRequest) -> server::HttpResponse {
+    let name: String = req.match_info().get("name").unwrap_or("World").into();
+    server::HttpResponse::Ok()
+        .body(sycamore::render_to_string(|ctx| sycamore::view! { ctx,
+            p { "Hello " (name) "!" }
+        }))
+}
+
+fn bootstrap() {
+    register_module(&Greet);
+    register_module(&GreetWithParam);
+}
 
 #[pagetop::main]
 async fn main() -> std::io::Result<()> {
-    server::run()?.await
+    server::run(Some(bootstrap))?.await
 }