diff --git a/src/app.py b/src/app.py
index 1cee4da..d605152 100644
--- a/src/app.py
+++ b/src/app.py
@@ -14,6 +14,7 @@ from myfasthtml.controls.TreeView import TreeView, TreeNode
 from myfasthtml.controls.helpers import Ids, mk
 from myfasthtml.core.instances import UniqueInstance
 from myfasthtml.icons.carbon import volume_object_storage
+from myfasthtml.icons.fluent_p2 import key_command16_regular
 from myfasthtml.icons.fluent_p3 import folder_open20_regular
 from myfasthtml.myfastapp import create_app
 
@@ -73,7 +74,7 @@ def create_sample_treeview(parent):
   tree_view.add_node(todo, parent_id=documents.id)
 
   # Expand all nodes to show the full structure
-  tree_view.expand_all()
+  #tree_view.expand_all()
 
   return tree_view
 
@@ -98,7 +99,7 @@ def index(session):
   
   commands_debugger = CommandsDebugger(layout)
   btn_show_commands_debugger = mk.label("Commands",
-                                        icon=None,
+                                        icon=key_command16_regular,
                                         command=add_tab("Commands", commands_debugger),
                                         id=commands_debugger.get_id())
   
diff --git a/src/myfasthtml/assets/myfasthtml.css b/src/myfasthtml/assets/myfasthtml.css
index 3e7568f..9bfe73f 100644
--- a/src/myfasthtml/assets/myfasthtml.css
+++ b/src/myfasthtml/assets/myfasthtml.css
@@ -492,6 +492,7 @@
     transition: background-color 0.15s ease;
     border-radius: 0.25rem;
 }
+
 /* Input for Editing */
 .mf-treenode-input {
     flex: 1;
@@ -503,7 +504,6 @@
 }
 
 
-
 .mf-treenode:hover {
     background-color: var(--color-base-200);
 }
@@ -544,4 +544,131 @@
 
 .mf-treenode:hover .mf-treenode-actions {
     display: flex;
-}
\ No newline at end of file
+}
+
+/* *********************************************** */
+/* ********** Generic Resizer Classes ************ */
+/* *********************************************** */
+
+/* Generic resizer - used by both Layout and Panel */
+.mf-resizer {
+    position: absolute;
+    width: 4px;
+    cursor: col-resize;
+    background-color: transparent;
+    transition: background-color 0.2s ease;
+    z-index: 100;
+    top: 0;
+    bottom: 0;
+}
+
+.mf-resizer:hover {
+    background-color: rgba(59, 130, 246, 0.3);
+}
+
+/* Active state during resize */
+.mf-resizing .mf-resizer {
+    background-color: rgba(59, 130, 246, 0.5);
+}
+
+/* Prevent text selection during resize */
+.mf-resizing {
+    user-select: none;
+    -webkit-user-select: none;
+    -moz-user-select: none;
+    -ms-user-select: none;
+}
+
+/* Cursor override for entire body during resize */
+.mf-resizing * {
+    cursor: col-resize !important;
+}
+
+/* Visual indicator for resizer on hover - subtle border */
+.mf-resizer::before {
+    content: '';
+    position: absolute;
+    top: 50%;
+    transform: translateY(-50%);
+    width: 2px;
+    height: 40px;
+    background-color: rgba(156, 163, 175, 0.4);
+    border-radius: 2px;
+    opacity: 0;
+    transition: opacity 0.2s ease;
+}
+
+.mf-resizer:hover::before,
+.mf-resizing .mf-resizer::before {
+    opacity: 1;
+}
+
+/* Resizer positioning */
+/* Left resizer is on the right side of the left panel */
+.mf-resizer-left {
+    right: 0;
+}
+
+/* Right resizer is on the left side of the right panel */
+.mf-resizer-right {
+    left: 0;
+}
+
+/* Position indicator for resizer */
+.mf-resizer-left::before {
+    right: 1px;
+}
+
+.mf-resizer-right::before {
+    left: 1px;
+}
+
+/* Disable transitions during resize for smooth dragging */
+.mf-item-resizing {
+    transition: none !important;
+}
+
+/* *********************************************** */
+/* *************** Panel Component *************** */
+/* *********************************************** */
+
+/* Container principal du panel */
+.mf-panel {
+    display: flex;
+    width: 100%;
+    height: 100%;
+    overflow: hidden;
+    position: relative;
+}
+
+/* Panel gauche */
+.mf-panel-left {
+    position: relative;
+    flex-shrink: 0;
+    width: 250px;
+    min-width: 150px;
+    max-width: 400px;
+    height: 100%;
+    overflow: auto;
+    border-right: 1px solid var(--color-border-primary);
+}
+
+/* Panel principal (centre) */
+.mf-panel-main {
+    flex: 1;
+    height: 100%;
+    overflow: auto;
+    min-width: 0; /* Important pour permettre le shrink du flexbox */
+}
+
+/* Panel droit */
+.mf-panel-right {
+    position: relative;
+    flex-shrink: 0;
+    width: 300px;
+    min-width: 150px;
+    max-width: 500px;
+    height: 100%;
+    overflow: auto;
+    border-left: 1px solid var(--color-border-primary);
+}
diff --git a/src/myfasthtml/assets/myfasthtml.js b/src/myfasthtml/assets/myfasthtml.js
index d0b0e5f..41715a9 100644
--- a/src/myfasthtml/assets/myfasthtml.js
+++ b/src/myfasthtml/assets/myfasthtml.js
@@ -1,40 +1,43 @@
 /**
- * Layout Drawer Resizer
+ * Generic Resizer
  *
- * Handles resizing of left and right drawers with drag functionality.
+ * Handles resizing of elements with drag functionality.
  * Communicates with server via HTMX to persist width changes.
+ * Works for both Layout drawers and Panel sides.
  */
 
 /**
- * Initialize drawer resizer functionality for a specific layout instance
+ * Initialize resizer functionality for a specific container
  *
- * @param {string} layoutId - The ID of the layout instance to initialize
+ * @param {string} containerId - The ID of the container instance to initialize
+ * @param {Object} options - Configuration options
+ * @param {number} options.minWidth - Minimum width in pixels (default: 150)
+ * @param {number} options.maxWidth - Maximum width in pixels (default: 600)
  */
-function initLayoutResizer(layoutId) {
-  'use strict';
+function initResizer(containerId, options = {}) {
 
-  const MIN_WIDTH = 150;
-  const MAX_WIDTH = 600;
+  const MIN_WIDTH = options.minWidth || 150;
+  const MAX_WIDTH = options.maxWidth || 600;
 
   let isResizing = false;
   let currentResizer = null;
-  let currentDrawer = null;
+  let currentItem = null;
   let startX = 0;
   let startWidth = 0;
   let side = null;
 
-  const layoutElement = document.getElementById(layoutId);
+  const containerElement = document.getElementById(containerId);
 
-  if (!layoutElement) {
-    console.error(`Layout element with ID "${layoutId}" not found`);
+  if (!containerElement) {
+    console.error(`Container element with ID "${containerId}" not found`);
     return;
   }
 
   /**
-   * Initialize resizer functionality for this layout instance
+   * Initialize resizer functionality for this container instance
    */
   function initResizers() {
-    const resizers = layoutElement.querySelectorAll('.mf-layout-resizer');
+    const resizers = containerElement.querySelectorAll('.mf-resizer');
 
     resizers.forEach(resizer => {
       // Remove existing listener if any to avoid duplicates
@@ -51,24 +54,24 @@ function initLayoutResizer(layoutId) {
 
     currentResizer = e.target;
     side = currentResizer.dataset.side;
-    currentDrawer = currentResizer.closest('.mf-layout-drawer');
+    currentItem = currentResizer.parentElement;
 
-    if (!currentDrawer) {
-      console.error('Could not find drawer element');
+    if (!currentItem) {
+      console.error('Could not find item element');
       return;
     }
 
     isResizing = true;
     startX = e.clientX;
-    startWidth = currentDrawer.offsetWidth;
+    startWidth = currentItem.offsetWidth;
 
     // Add event listeners for mouse move and up
     document.addEventListener('mousemove', handleMouseMove);
     document.addEventListener('mouseup', handleMouseUp);
 
     // Add resizing class for visual feedback
-    document.body.classList.add('mf-layout-resizing');
-    currentDrawer.classList.add('mf-layout-drawer-resizing');
+    document.body.classList.add('mf-resizing');
+    currentItem.classList.add('mf-item-resizing');
   }
 
   /**
@@ -92,8 +95,8 @@ function initLayoutResizer(layoutId) {
     // Constrain width between min and max
     newWidth = Math.max(MIN_WIDTH, Math.min(MAX_WIDTH, newWidth));
 
-    // Update drawer width visually
-    currentDrawer.style.width = `${newWidth}px`;
+    // Update item width visually
+    currentItem.style.width = `${newWidth}px`;
   }
 
   /**
@@ -109,11 +112,11 @@ function initLayoutResizer(layoutId) {
     document.removeEventListener('mouseup', handleMouseUp);
 
     // Remove resizing classes
-    document.body.classList.remove('mf-layout-resizing');
-    currentDrawer.classList.remove('mf-layout-drawer-resizing');
+    document.body.classList.remove('mf-resizing');
+    currentItem.classList.remove('mf-item-resizing');
 
     // Get final width
-    const finalWidth = currentDrawer.offsetWidth;
+    const finalWidth = currentItem.offsetWidth;
     const commandId = currentResizer.dataset.commandId;
 
     if (!commandId) {
@@ -122,24 +125,24 @@ function initLayoutResizer(layoutId) {
     }
 
     // Send width update to server
-    saveDrawerWidth(commandId, finalWidth);
+    saveWidth(commandId, finalWidth);
 
     // Reset state
     currentResizer = null;
-    currentDrawer = null;
+    currentItem = null;
     side = null;
   }
 
   /**
-   * Save drawer width to server via HTMX
+   * Save width to server via HTMX
    */
-  function saveDrawerWidth(commandId, width) {
+  function saveWidth(commandId, width) {
     htmx.ajax('POST', '/myfasthtml/commands', {
       headers: {
         "Content-Type": "application/x-www-form-urlencoded"
       },
       swap: "outerHTML",
-      target: `#${currentDrawer.id}`,
+      target: `#${currentItem.id}`,
       values: {
         c_id: commandId,
         width: width
@@ -150,8 +153,8 @@ function initLayoutResizer(layoutId) {
   // Initialize resizers
   initResizers();
 
-  // Re-initialize after HTMX swaps within this layout
-  layoutElement.addEventListener('htmx:afterSwap', function (event) {
+  // Re-initialize after HTMX swaps within this container
+  containerElement.addEventListener('htmx:afterSwap', function (event) {
     initResizers();
   });
 }
diff --git a/src/myfasthtml/controls/InstancesDebugger.py b/src/myfasthtml/controls/InstancesDebugger.py
index fcec443..cda50e1 100644
--- a/src/myfasthtml/controls/InstancesDebugger.py
+++ b/src/myfasthtml/controls/InstancesDebugger.py
@@ -1,3 +1,4 @@
+from myfasthtml.controls.Panel import Panel
 from myfasthtml.controls.VisNetwork import VisNetwork
 from myfasthtml.core.instances import SingleInstance, InstancesManager
 from myfasthtml.core.network_utils import from_parent_child_list
@@ -6,9 +7,14 @@ from myfasthtml.core.network_utils import from_parent_child_list
 class InstancesDebugger(SingleInstance):
   def __init__(self, parent, _id=None):
     super().__init__(parent, _id=_id)
+    self._panel = Panel(self, _id="-panel")
   
   def render(self):
-    s_name = InstancesManager.get_session_user_name
+    nodes, edges = self._get_nodes_and_edges()
+    vis_network = VisNetwork(self, nodes=nodes, edges=edges, _id="-vis")
+    return self._panel.set_main(vis_network)
+  
+  def _get_nodes_and_edges(self):
     instances = self._get_instances()
     nodes, edges = from_parent_child_list(
       instances,
@@ -23,9 +29,7 @@ class InstancesDebugger(SingleInstance):
     for node in nodes:
       node["shape"] = "box"
     
-    vis_network = VisNetwork(self, nodes=nodes, edges=edges, _id="-vis")
-    # vis_network.add_to_options(physics={"wind": {"x": 0, "y": 1}})
-    return vis_network
+    return nodes, edges
   
   def _get_instances(self):
     return list(InstancesManager.instances.values())
diff --git a/src/myfasthtml/controls/Layout.py b/src/myfasthtml/controls/Layout.py
index 264329f..0c00d0a 100644
--- a/src/myfasthtml/controls/Layout.py
+++ b/src/myfasthtml/controls/Layout.py
@@ -123,6 +123,7 @@ class Layout(SingleInstance):
     self.header_right = self.Content(self)
     self.footer_left = self.Content(self)
     self.footer_right = self.Content(self)
+    self._footer_content = None
   
   def set_footer(self, content):
     """
@@ -141,6 +142,7 @@ class Layout(SingleInstance):
         content: FastHTML component(s) or content for the main area
     """
     self._main_content = content
+    return self
   
   def toggle_drawer(self, side: Literal["left", "right"]):
     logger.debug(f"Toggle drawer: {side=}, {self._state.left_drawer_open=}")
@@ -233,7 +235,7 @@ class Layout(SingleInstance):
         Div: FastHTML Div component for left drawer
     """
     resizer = Div(
-      cls="mf-layout-resizer mf-layout-resizer-right",
+      cls="mf-resizer mf-resizer-left",
       data_command_id=self.commands.update_drawer_width("left").id,
       data_side="left"
     )
@@ -266,8 +268,9 @@ class Layout(SingleInstance):
     Returns:
         Div: FastHTML Div component for right drawer
     """
+    
     resizer = Div(
-      cls="mf-layout-resizer mf-layout-resizer-left",
+      cls="mf-resizer mf-resizer-right",
       data_command_id=self.commands.update_drawer_width("right").id,
       data_side="right"
     )
@@ -311,7 +314,7 @@ class Layout(SingleInstance):
       self._mk_main(),
       self._mk_right_drawer(),
       self._mk_footer(),
-      Script(f"initLayoutResizer('{self._id}');"),
+      Script(f"initResizer('{self._id}');"),
       id=self._id,
       cls="mf-layout",
     )
diff --git a/src/myfasthtml/controls/Panel.py b/src/myfasthtml/controls/Panel.py
new file mode 100644
index 0000000..66a2bbf
--- /dev/null
+++ b/src/myfasthtml/controls/Panel.py
@@ -0,0 +1,102 @@
+from dataclasses import dataclass
+from typing import Literal
+
+from fasthtml.components import Div
+from fasthtml.xtend import Script
+
+from myfasthtml.controls.BaseCommands import BaseCommands
+from myfasthtml.core.commands import Command
+from myfasthtml.core.instances import MultipleInstance
+
+
+@dataclass
+class PanelConf:
+  left: bool = False
+  right: bool = True
+
+
+class Commands(BaseCommands):
+  def toggle_side(self, side: Literal["left", "right"]):
+    return Command("TogglePanelSide", f"Toggle {side} side panel", self._owner.toggle_side, side)
+  
+  def update_side_width(self, side: Literal["left", "right"]):
+    """
+    Create a command to update panel's side width.
+
+    Args:
+        side: Which panel's side to update ("left" or "right")
+
+    Returns:
+        Command: Command object for updating panel's side width
+    """
+    return Command(
+      f"UpdatePanelSideWidth_{side}",
+      f"Update {side} side panel width",
+      self._owner.update_side_width,
+      side
+    )
+
+
+class Panel(MultipleInstance):
+  def __init__(self, parent, conf=None, _id=None):
+    super().__init__(parent, _id=_id)
+    self.conf = conf or PanelConf()
+    self.commands = Commands(self)
+    self._main = None
+    self._right = None
+    self._left = None
+  
+  def update_side_width(self, side, width):
+    pass
+  
+  def toggle_side(self, side):
+    pass
+  
+  def set_main(self, main):
+    self._main = main
+    return self
+  
+  def set_right(self, right):
+    self._right = right
+    return self
+  
+  def set_left(self, left):
+    self._left = left
+    return self
+  
+  def _mk_right(self):
+    if not self.conf.right:
+      return None
+
+    resizer = Div(
+      cls="mf-resizer mf-resizer-right",
+      data_command_id=self.commands.update_side_width("right").id,
+      data_side="right"
+    )
+
+    return Div(resizer, self._right, cls="mf-panel-right")
+
+  def _mk_left(self):
+    if not self.conf.left:
+      return None
+
+    resizer = Div(
+      cls="mf-resizer mf-resizer-left",
+      data_command_id=self.commands.update_side_width("left").id,
+      data_side="left"
+    )
+
+    return Div(self._left, resizer, cls="mf-panel-left")
+  
+  def render(self):
+    return Div(
+      self._mk_left(),
+      Div(self._main, cls="mf-panel-main"),
+      self._mk_right(),
+      Script(f"initResizer('{self._id}');"),
+      cls="mf-panel",
+      id=self._id,
+    )
+  
+  def __ft__(self):
+    return self.render()
diff --git a/src/myfasthtml/test/matcher.py b/src/myfasthtml/test/matcher.py
index b127fcb..5b313cb 100644
--- a/src/myfasthtml/test/matcher.py
+++ b/src/myfasthtml/test/matcher.py
@@ -409,11 +409,25 @@ def matches(actual, expected, path=""):
       assert hasattr(actual, attr), _error_msg(f"'{attr}' is not found in Actual.",
                                                _actual=actual,
                                                _expected=expected)
-      assert matches(getattr(actual, attr), value), _error_msg(f"The values are different for '{attr}': ",
-                                                               _actual=getattr(actual, attr),
-                                                               _expected=value)
+      try:
+        matches(getattr(actual, attr), value)
+      except AssertionError as e:
+        match = re.search(r"Error : (.+?)\n", str(e))
+        if match:
+          assert False, _error_msg(f"{match.group(1)} for '{attr}':",
+                                   _actual=getattr(actual, attr),
+                                   _expected=value)
+        assert False, _error_msg(f"The values are different for '{attr}': ",
+                                 _actual=getattr(actual, attr),
+                                 _expected=value)
     return True
   
+  if isinstance(expected, Predicate):
+    assert expected.validate(actual), \
+      _error_msg(f"The condition '{expected}' is not satisfied.",
+                 _actual=actual,
+                 _expected=expected)
+  
   assert _type(actual) == _type(expected) or (hasattr(actual, "tag") and hasattr(expected, "tag")), \
     _error_msg("The types are different: ", _actual=actual, _expected=expected)
   
@@ -481,7 +495,7 @@ def matches(actual, expected, path=""):
   
   
   else:
-    assert actual == expected, _error_msg("The values are different: ",
+    assert actual == expected, _error_msg("The values are different",
                                           _actual=actual,
                                           _expected=expected)
   
diff --git a/tests/testclient/test_matches.py b/tests/testclient/test_matches.py
index b4db012..b24fdf5 100644
--- a/tests/testclient/test_matches.py
+++ b/tests/testclient/test_matches.py
@@ -93,6 +93,7 @@ class TestMatches:
       (Div(Dummy(123, "value")), Div(TestObject(Dummy, attr1=123, attr3="value3")), "'attr3' is not found in Actual"),
       (Div(Dummy(123, "value")), Div(TestObject(Dummy, attr1=123, attr2="value2")), "are different for 'attr2'"),
       (Div(123, "value"), TestObject("Dummy", attr1=123, attr2="value2"), "The types are different:"),
+      (Dummy(123, "value"), TestObject("Dummy", attr1=123, attr2=Contains("value2")), "The condition 'Contains(value2)' is not satisfied"),
   
   ])
   def test_i_can_detect_errors(self, actual, expected, error_message):