diff --git a/core/src/constants.rs b/core/src/constants.rs
index 23c70b8..954a52d 100644
--- a/core/src/constants.rs
+++ b/core/src/constants.rs
@@ -1,4 +1,4 @@
-//! Constant variables.
+//! Constant variables for UI.
 
 pub static WHITE: u32 = 0xffffff;
 pub static _RED: u32 = 0xff0000;
diff --git a/core/src/renderer/dom/mod.rs b/core/src/renderer/dom/mod.rs
index 128ecfd..1f70a6c 100644
--- a/core/src/renderer/dom/mod.rs
+++ b/core/src/renderer/dom/mod.rs
@@ -4,3 +4,4 @@
 pub mod activation_behavior;
 pub mod api;
 pub mod event;
+pub mod window;
diff --git a/core/src/renderer/dom/window.rs b/core/src/renderer/dom/window.rs
new file mode 100644
index 0000000..898426e
--- /dev/null
+++ b/core/src/renderer/dom/window.rs
@@ -0,0 +1,41 @@
+//! This is a DOM Window object.
+//! https://html.spec.whatwg.org/multipage/nav-history-apis.html#window
+
+use crate::browser::Browser;
+use crate::renderer::html::dom::Node;
+use crate::renderer::html::dom::NodeKind;
+use crate::renderer::page::Page;
+use alloc::rc::Rc;
+use alloc::rc::Weak;
+use core::cell::RefCell;
+
+/// https://html.spec.whatwg.org/multipage/nav-history-apis.html#window
+///
+/// https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/frame/dom_window.h
+#[derive(Debug, Clone)]
+pub struct Window {
+    _browser: Weak<RefCell<Browser>>,
+    _page: Weak<RefCell<Page>>,
+    pub document: Rc<RefCell<Node>>,
+}
+
+impl Window {
+    pub fn new(browser: Weak<RefCell<Browser>>) -> Self {
+        let window = Self {
+            _browser: browser,
+            _page: Weak::new(),
+            document: Rc::new(RefCell::new(Node::new(NodeKind::Document))),
+        };
+
+        window
+            .document
+            .borrow_mut()
+            .set_window(Rc::downgrade(&Rc::new(RefCell::new(window.clone()))));
+
+        window
+    }
+
+    pub fn document(&self) -> Rc<RefCell<Node>> {
+        self.document.clone()
+    }
+}
diff --git a/core/src/renderer/html/dom.rs b/core/src/renderer/html/dom.rs
index 4fe697e..d0f5dfc 100644
--- a/core/src/renderer/html/dom.rs
+++ b/core/src/renderer/html/dom.rs
@@ -8,9 +8,9 @@ use crate::renderer::dom::event::Event;
 use crate::renderer::dom::event::EventListener;
 use crate::renderer::dom::event::EventListenerCallback;
 use crate::renderer::dom::event::EventTarget;
+use crate::renderer::dom::window::Window;
 use crate::renderer::html::attribute::Attribute;
 use crate::renderer::html::token::{HtmlToken, HtmlTokenizer, State};
-use crate::renderer::page::Page;
 use crate::utils::console_warning;
 use alloc::format;
 use alloc::rc::{Rc, Weak};
@@ -20,32 +20,6 @@ use core::cell::RefCell;
 use core::fmt::{Display, Formatter};
 use core::str::FromStr;
 
-#[derive(Debug, Clone)]
-/// https://html.spec.whatwg.org/multipage/nav-history-apis.html#window
-pub struct Window {
-    _browser: Weak<RefCell<Browser>>,
-    _page: Weak<RefCell<Page>>,
-    document: Rc<RefCell<Node>>,
-}
-
-impl Window {
-    pub fn new(browser: Weak<RefCell<Browser>>) -> Self {
-        let window = Self {
-            _browser: browser,
-            _page: Weak::new(),
-            document: Rc::new(RefCell::new(Node::new(NodeKind::Document))),
-        };
-
-        window.document.borrow_mut().window = Rc::downgrade(&Rc::new(RefCell::new(window.clone())));
-
-        window
-    }
-
-    pub fn document(&self) -> Rc<RefCell<Node>> {
-        self.document.clone()
-    }
-}
-
 #[derive(Debug, Clone)]
 /// https://dom.spec.whatwg.org/#interface-node
 pub struct Node {
@@ -82,6 +56,10 @@ impl Node {
         self.kind.clone()
     }
 
+    pub fn set_window(&mut self, window: Weak<RefCell<Window>>) {
+        self.window = window;
+    }
+
     pub fn get_window(&self) -> Weak<RefCell<Window>> {
         if self.window.upgrade().is_some() {
             return self.window.clone();
diff --git a/core/src/renderer/page.rs b/core/src/renderer/page.rs
index 1940b2b..c008aff 100644
--- a/core/src/renderer/page.rs
+++ b/core/src/renderer/page.rs
@@ -1,7 +1,9 @@
 //! This is corresponding to a page.
 //!
-//! https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/frame/
-//! https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/frame/local_frame_view.h
+//! In Chromium, a page can contain multiple frames (iframe, etc.), but this browser has one frame per page. This module implements a subset of Page and Frame.
+//! https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/page/page.h
+//! https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/frame/frame.h
+//! https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/frame/local_frame.h
 
 use crate::alloc::string::ToString;
 use crate::browser::Browser;
@@ -11,8 +13,8 @@ use crate::renderer::css::cssom::CssParser;
 use crate::renderer::css::cssom::StyleSheet;
 use crate::renderer::css::token::CssTokenizer;
 use crate::renderer::dom::api::{get_js_content, get_style_content};
+use crate::renderer::dom::window::Window;
 use crate::renderer::html::dom::HtmlParser;
-use crate::renderer::html::dom::Window;
 use crate::renderer::html::html_builder::dom_to_html;
 use crate::renderer::html::token::HtmlTokenizer;
 use crate::renderer::js::ast::JsParser;
@@ -45,6 +47,7 @@ impl Subresource {
 pub struct Page {
     browser: Weak<RefCell<Browser>>,
     url: Option<String>,
+    /// https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/frame/frame.h;drc=ac83a5a2d3c04763d86ce16d92f3904cc9566d3a;bpv=1;bpt=1;l=505
     window: Option<Rc<RefCell<Window>>>,
     style: Option<StyleSheet>,
     layout_view: Option<LayoutView>,