diff --git a/src/myfasthtml/controls/DataGridsManager.py b/src/myfasthtml/controls/DataGridsManager.py
index 8c7d18c..f5e4fb1 100644
--- a/src/myfasthtml/controls/DataGridsManager.py
+++ b/src/myfasthtml/controls/DataGridsManager.py
@@ -50,7 +50,7 @@ class Commands(BaseCommands):
     return Command("NewGrid",
                    "New grid",
                    self._owner,
-                   self._owner.new_grid)
+                   self._owner.new_grid).htmx(target=f"#{self._owner._tree.get_id()}")
   
   def open_from_excel(self, tab_id, file_upload):
     return Command("OpenFromExcel",
@@ -104,6 +104,62 @@ class DataGridsManager(SingleInstance, DatagridMetadataProvider):
     file_upload.set_on_ok(self.commands.open_from_excel(tab_id, file_upload))
     return self._tabs_manager.show_tab(tab_id)
   
+  def new_grid(self):
+    selected_id = self._tree.get_selected_id()
+
+    if selected_id is None:
+      parent_id = self._tree.ensure_path("Untitled")
+    else:
+      node = self._tree._state.items[selected_id]
+      if node.type == "folder":
+        parent_id = selected_id
+      else:  # leaf
+        parent_id = node.parent
+
+    namespace = self._tree._state.items[parent_id].label
+    name = self._generate_unique_sheet_name(parent_id)
+
+    dg_conf = DatagridConf(namespace=namespace, name=name)
+    dg = DataGrid(self, conf=dg_conf, save_state=True)
+    dg.init_from_dataframe(pd.DataFrame())
+    self._registry.put(namespace, name, dg.get_id())
+
+    tab_id = self._tabs_manager.create_tab(name, dg)
+    document = DocumentDefinition(
+      document_id=str(uuid.uuid4()),
+      namespace=namespace,
+      name=name,
+      type="excel",
+      tab_id=tab_id,
+      datagrid_id=dg.get_id()
+    )
+    self._state.elements = self._state.elements + [document]
+
+    tree_node = TreeNode(
+      id=document.document_id,
+      label=name,
+      type="excel",
+      parent=parent_id,
+      bag=document.document_id
+    )
+    self._tree.add_node(tree_node, parent_id=parent_id)
+
+    if parent_id not in self._tree._state.opened:
+      self._tree._state.opened.append(parent_id)
+
+    self._tree._state.selected = document.document_id
+    self._tree._start_rename(document.document_id)
+
+    return self._tree, self._tabs_manager.show_tab(tab_id)
+
+  def _generate_unique_sheet_name(self, parent_id: str) -> str:
+    children = self._tree._state.items[parent_id].children
+    existing_labels = {self._tree._state.items[c].label for c in children}
+    n = 1
+    while f"Sheet{n}" in existing_labels:
+      n += 1
+    return f"Sheet{n}"
+
   def open_from_excel(self, tab_id, file_upload: FileUpload):
     excel_content = file_upload.get_content()
     df = pd.read_excel(BytesIO(excel_content), file_upload.get_sheet_name())
@@ -257,7 +313,7 @@ class DataGridsManager(SingleInstance, DatagridMetadataProvider):
   def mk_main_icons(self):
     return Div(
       mk.icon(folder_open20_regular, tooltip="Upload from source", command=self.commands.upload_from_source()),
-      mk.icon(table_add20_regular, tooltip="New grid", command=self.commands.clear_tree()),
+      mk.icon(table_add20_regular, tooltip="New grid", command=self.commands.new_grid()),
       cls="flex"
     )
   
diff --git a/src/myfasthtml/controls/TreeView.py b/src/myfasthtml/controls/TreeView.py
index 3dc8417..df99050 100644
--- a/src/myfasthtml/controls/TreeView.py
+++ b/src/myfasthtml/controls/TreeView.py
@@ -184,10 +184,10 @@ class TreeView(MultipleInstance):
     self._state = TreeViewState(self)
     self.conf = conf or TreeViewConf()
     self.commands = Commands(self)
-
+    
     if items:
       self._state.items = items
-
+    
     if self.conf.icons:
       self._state.icon_config = self.conf.icons
   
@@ -350,6 +350,7 @@ class TreeView(MultipleInstance):
   
   def _save_rename(self, node_id: str, node_label: str):
     """Save renamed node with new label."""
+    logger.debug(f"_save_rename {node_id=}, {node_label=}")
     if node_id not in self._state.items:
       raise ValueError(f"Node {node_id} does not exist")
     
@@ -393,7 +394,9 @@ class TreeView(MultipleInstance):
     """Select a node."""
     if node_id not in self._state.items:
       raise ValueError(f"Node {node_id} does not exist")
-    
+
+    # Cancel edit mode when selecting
+    self._state.editing = None
     self._state.selected = node_id
     return self
   
@@ -401,11 +404,11 @@ class TreeView(MultipleInstance):
     """Render action buttons for a node (visible on hover)."""
     is_leaf = len(self._state.items[node_id].children) == 0
     conf = self.conf
-
-    add_visible    = conf.add_leaf    if is_leaf else conf.add_node
-    edit_visible   = conf.edit_leaf   if is_leaf else conf.edit_node
+    
+    add_visible = conf.add_leaf if is_leaf else conf.add_node
+    edit_visible = conf.edit_leaf if is_leaf else conf.edit_node
     delete_visible = conf.delete_leaf if is_leaf else conf.delete_node
-
+    
     buttons = []
     if add_visible:
       buttons.append(mk.icon(add_circle20_regular, command=self.commands.add_child(node_id)))
@@ -413,7 +416,7 @@ class TreeView(MultipleInstance):
       buttons.append(mk.icon(edit20_regular, command=self.commands.start_rename(node_id)))
     if delete_visible:
       buttons.append(mk.icon(delete20_regular, command=self.commands.delete_node(node_id)))
-
+    
     return Div(*buttons, cls="mf-treenode-actions")
   
   def _render_node(self, node_id: str, level: int = 0):
diff --git a/tests/controls/test_datagridmanager.py b/tests/controls/test_datagridmanager.py
new file mode 100644
index 0000000..92375ee
--- /dev/null
+++ b/tests/controls/test_datagridmanager.py
@@ -0,0 +1,261 @@
+"""Unit tests for DataGridsManager component."""
+import shutil
+
+import pytest
+
+from myfasthtml.controls.DataGridsManager import DataGridsManager
+from myfasthtml.controls.TabsManager import TabsManager
+from myfasthtml.controls.TreeView import TreeNode
+from myfasthtml.core.instances import InstancesManager
+from .conftest import root_instance
+
+
+@pytest.fixture(autouse=True)
+def cleanup_db():
+  shutil.rmtree(".myFastHtmlDb", ignore_errors=True)
+
+
+@pytest.fixture
+def datagrid_manager(root_instance):
+  """Create a DataGridsManager instance for testing."""
+  InstancesManager.reset()
+  TabsManager(root_instance)  # just define it
+  return DataGridsManager(root_instance)
+
+
+class TestDataGridsManagerBehaviour:
+  """Tests for DataGridsManager behavior and logic."""
+  
+  def test_i_can_create_new_grid_with_nothing_selected(self, datagrid_manager):
+    """Test creating a new grid when no node is selected.
+
+    Verifies that:
+    - Grid is created under "Untitled" folder
+    - Name is "Sheet1"
+    - Node is selected and in edit mode
+    - Document definition is created
+    """
+    result = datagrid_manager.new_grid()
+    
+    # Verify tree structure
+    tree = datagrid_manager._tree
+    assert len(tree._state.items) == 2, "Should have Untitled folder + Sheet1 node"
+    
+    # Find the Untitled folder and Sheet1 node
+    nodes = list(tree._state.items.values())
+    untitled = [n for n in nodes if n.label == "Untitled"][0]
+    sheet = [n for n in nodes if n.label == "Sheet1"][0]
+    
+    # Verify hierarchy
+    assert untitled.parent is None, "Untitled should be root"
+    assert sheet.parent == untitled.id, "Sheet1 should be under Untitled"
+    
+    # Verify selection and edit mode
+    assert tree._state.selected == sheet.id, "Sheet1 should be selected"
+    assert tree._state.editing == sheet.id, "Sheet1 should be in edit mode"
+    
+    # Verify document definition
+    assert len(datagrid_manager._state.elements) == 1, "Should have one document"
+    doc = datagrid_manager._state.elements[0]
+    assert doc.namespace == "Untitled"
+    assert doc.name == "Sheet1"
+    assert doc.type == "excel"
+  
+  def test_i_can_create_new_grid_under_selected_folder(self, datagrid_manager):
+    """Test creating a new grid when a folder is selected.
+
+    Verifies that:
+    - Grid is created under the selected folder
+    - Namespace matches folder name
+    """
+    # Create a folder and select it
+    folder_id = datagrid_manager._tree.ensure_path("MyFolder")
+    datagrid_manager._tree._select_node(folder_id)
+    
+    result = datagrid_manager.new_grid()
+    
+    # Verify the new grid is under MyFolder
+    tree = datagrid_manager._tree
+    nodes = list(tree._state.items.values())
+    sheet = [n for n in nodes if n.label == "Sheet1"][0]
+    
+    assert sheet.parent == folder_id, "Sheet1 should be under MyFolder"
+    
+    # Verify document definition
+    doc = datagrid_manager._state.elements[0]
+    assert doc.namespace == "MyFolder"
+    assert doc.name == "Sheet1"
+  
+  def test_i_can_create_new_grid_under_selected_leaf_parent(self, datagrid_manager):
+    """Test creating a new grid when a leaf node is selected.
+
+    Verifies that:
+    - Grid is created under the parent of the selected leaf
+    - Not under the leaf itself
+    """
+    # Create a folder with a leaf
+    folder_id = datagrid_manager._tree.ensure_path("MyFolder")
+    leaf = TreeNode(label="ExistingSheet", type="excel", parent=folder_id)
+    datagrid_manager._tree.add_node(leaf, parent_id=folder_id)
+    
+    # Select the leaf
+    datagrid_manager._tree._select_node(leaf.id)
+    
+    result = datagrid_manager.new_grid()
+    
+    # Verify the new grid is under MyFolder (not under ExistingSheet)
+    tree = datagrid_manager._tree
+    nodes = list(tree._state.items.values())
+    new_sheet = [n for n in nodes if n.label == "Sheet1"][0]
+    
+    assert new_sheet.parent == folder_id, "Sheet1 should be under MyFolder (leaf's parent)"
+    assert new_sheet.parent != leaf.id, "Sheet1 should not be under the leaf"
+  
+  def test_new_grid_generates_unique_sheet_names(self, datagrid_manager):
+    """Test that new_grid generates unique sequential sheet names.
+
+    Verifies Sheet1, Sheet2, Sheet3... generation.
+    """
+    # Create first grid
+    datagrid_manager.new_grid()
+    assert datagrid_manager._state.elements[0].name == "Sheet1"
+    
+    # Create second grid
+    datagrid_manager.new_grid()
+    assert datagrid_manager._state.elements[1].name == "Sheet2"
+    
+    # Create third grid
+    datagrid_manager.new_grid()
+    assert datagrid_manager._state.elements[2].name == "Sheet3"
+  
+  def test_new_grid_expands_parent_folder(self, datagrid_manager):
+    """Test that creating a new grid automatically expands the parent folder.
+
+    Verifies parent is added to tree._state.opened.
+    """
+    result = datagrid_manager.new_grid()
+    
+    tree = datagrid_manager._tree
+    nodes = list(tree._state.items.values())
+    untitled = [n for n in nodes if n.label == "Untitled"][0]
+    
+    # Verify parent is expanded
+    assert untitled.id in tree._state.opened, "Parent folder should be expanded"
+  
+  def test_new_grid_selects_and_edits_new_node(self, datagrid_manager):
+    """Test that new grid node is both selected and in edit mode.
+
+    Verifies _state.selected and _state.editing are set to new node.
+    """
+    result = datagrid_manager.new_grid()
+    
+    tree = datagrid_manager._tree
+    nodes = list(tree._state.items.values())
+    sheet = [n for n in nodes if n.label == "Sheet1"][0]
+    
+    # Verify selection
+    assert tree._state.selected == sheet.id, "New node should be selected"
+    
+    # Verify edit mode
+    assert tree._state.editing == sheet.id, "New node should be in edit mode"
+  
+  def test_new_grid_creates_document_definition(self, datagrid_manager):
+    """Test that new_grid creates a DocumentDefinition with correct fields.
+
+    Verifies document_id, namespace, name, type, tab_id, datagrid_id.
+    """
+    result = datagrid_manager.new_grid()
+    
+    # Verify document was created
+    assert len(datagrid_manager._state.elements) == 1, "Should have one document"
+    
+    doc = datagrid_manager._state.elements[0]
+    
+    # Verify all fields
+    assert doc.document_id is not None, "Should have document_id"
+    assert isinstance(doc.document_id, str), "document_id should be string"
+    assert doc.namespace == "Untitled", "namespace should match parent folder"
+    assert doc.name == "Sheet1", "name should be Sheet1"
+    assert doc.type == "excel", "type should be excel"
+    assert doc.tab_id is not None, "Should have tab_id"
+    assert doc.datagrid_id is not None, "Should have datagrid_id"
+  
+  def test_new_grid_creates_datagrid_and_registers(self, datagrid_manager):
+    """Test that new_grid creates a DataGrid and registers it.
+
+    Verifies DataGrid exists and is in registry with namespace.name.
+    """
+    result = datagrid_manager.new_grid()
+    
+    doc = datagrid_manager._state.elements[0]
+    
+    # Verify DataGrid is registered
+    tables = datagrid_manager._registry.get_all_tables()
+    assert "Untitled.Sheet1" in tables, "DataGrid should be registered as Untitled.Sheet1"
+    
+    # Verify DataGrid exists in InstancesManager
+    from myfasthtml.core.instances import InstancesManager
+    datagrid = InstancesManager.get(datagrid_manager._session, doc.datagrid_id, None)
+    assert datagrid is not None, "DataGrid instance should exist"
+  
+  def test_new_grid_creates_tab_with_datagrid(self, datagrid_manager):
+    """Test that new_grid creates a tab with correct label and content.
+
+    Verifies tab is created via TabsManager with DataGrid as content.
+    """
+    result = datagrid_manager.new_grid()
+    
+    doc = datagrid_manager._state.elements[0]
+    tabs_manager = datagrid_manager._tabs_manager
+    
+    # Verify tab exists in TabsManager
+    assert doc.tab_id in tabs_manager._state.tabs, "Tab should exist in TabsManager"
+    
+    # Verify tab label
+    tab_metadata = tabs_manager._state.tabs[doc.tab_id]
+    assert tab_metadata['label'] == "Sheet1", "Tab label should be Sheet1"
+  
+  def test_generate_unique_sheet_name_with_no_children(self, datagrid_manager):
+    """Test _generate_unique_sheet_name on an empty folder.
+
+    Verifies it returns "Sheet1" when no children exist.
+    """
+    folder_id = datagrid_manager._tree.ensure_path("EmptyFolder")
+    
+    name = datagrid_manager._generate_unique_sheet_name(folder_id)
+    
+    assert name == "Sheet1", "Should generate Sheet1 for empty folder"
+  
+  def test_generate_unique_sheet_name_with_existing_sheets(self, datagrid_manager):
+    """Test _generate_unique_sheet_name with existing sheets.
+
+    Verifies it generates the next sequential number.
+    """
+    folder_id = datagrid_manager._tree.ensure_path("MyFolder")
+    
+    # Add Sheet1 and Sheet2 manually
+    sheet1 = TreeNode(label="Sheet1", type="excel", parent=folder_id)
+    sheet2 = TreeNode(label="Sheet2", type="excel", parent=folder_id)
+    datagrid_manager._tree.add_node(sheet1, parent_id=folder_id)
+    datagrid_manager._tree.add_node(sheet2, parent_id=folder_id)
+    
+    name = datagrid_manager._generate_unique_sheet_name(folder_id)
+    
+    assert name == "Sheet3", "Should generate Sheet3 when Sheet1 and Sheet2 exist"
+  
+  def test_generate_unique_sheet_name_skips_gaps(self, datagrid_manager):
+    """Test _generate_unique_sheet_name fills gaps in sequence.
+
+    Verifies it generates Sheet2 when Sheet1 and Sheet3 exist (missing Sheet2).
+    """
+    folder_id = datagrid_manager._tree.ensure_path("MyFolder")
+    
+    # Add Sheet1 and Sheet3 (skip Sheet2)
+    sheet1 = TreeNode(label="Sheet1", type="excel", parent=folder_id)
+    sheet3 = TreeNode(label="Sheet3", type="excel", parent=folder_id)
+    datagrid_manager._tree.add_node(sheet1, parent_id=folder_id)
+    datagrid_manager._tree.add_node(sheet3, parent_id=folder_id)
+    
+    name = datagrid_manager._generate_unique_sheet_name(folder_id)
+    
+    assert name == "Sheet2", "Should generate Sheet2 to fill the gap"
diff --git a/tests/controls/test_treeview.py b/tests/controls/test_treeview.py
index 90af53c..76b1f5b 100644
--- a/tests/controls/test_treeview.py
+++ b/tests/controls/test_treeview.py
@@ -583,6 +583,44 @@ class TestTreeviewBehaviour:
     assert len(tree_view._state.items) == 1, "Node should not have been added to items"
     assert tree_view._state.items[node1.id] == node2, "Node should not have been replaced"
 
+  def test_selecting_node_cancels_edit_mode(self, root_instance):
+    """Test that selecting a node cancels any active edit mode."""
+    tree_view = TreeView(root_instance)
+    node1 = TreeNode(label="Node 1", type="folder")
+    node2 = TreeNode(label="Node 2", type="folder")
+
+    tree_view.add_node(node1)
+    tree_view.add_node(node2)
+
+    # Start editing node1
+    tree_view._start_rename(node1.id)
+    assert tree_view._state.editing == node1.id
+
+    # Select node2
+    tree_view._select_node(node2.id)
+
+    # Edit mode should be cancelled
+    assert tree_view._state.editing is None
+    assert tree_view._state.selected == node2.id
+
+  def test_selecting_same_editing_node_cancels_edit_mode(self, root_instance):
+    """Test that selecting the same node being edited cancels edit mode."""
+    tree_view = TreeView(root_instance)
+    node = TreeNode(label="Node", type="folder")
+
+    tree_view.add_node(node)
+
+    # Start editing the node
+    tree_view._start_rename(node.id)
+    assert tree_view._state.editing == node.id
+
+    # Select the same node
+    tree_view._select_node(node.id)
+
+    # Edit mode should be cancelled
+    assert tree_view._state.editing is None
+    assert tree_view._state.selected == node.id
+
 
 class TestTreeViewRender:
   """Tests for TreeView HTML rendering."""