DomHelper to create new collapsible Panel

[tej]

Hi,

I'm new to ExtJs and I'm trying to create a collapsible panel and would like to insert it into the Dom. I'm doing it as follows:

            
           this.foo_holder = Ext.DomHelper.append(document.body, [{id : 'testdiv'}]);

           var fooPanel = {
              xtype         : 'panel',
              height        : 100,
              title         : 'fooPanel',
              titleCollapse : true,
              collapsed     : true,
              collapsible   : true,
              html          : 'Blah Blah'
            };

            Ext.DomHelper.append(this.foo_holder, fooPanel);

However, it just shows up the html when the panel is inserted. I don't see any title bar or title or any collapsible functionality.
When I create the same panel before the dom is rendered, it shows up properly. But I need to add/remove panels later on.

Can anyone help ?