How to open a Panel on Button click

I want to open a panel window under the button i click which is located in the header. The panel should be displayed under the button (aligned with the header) : i try :

{
            xtype:'button',
            height: '100%',
            text: Strings.Notifications,
            glyph: 'xf142@FontAwesome',
            reference: 'settingsNotificationsButton',
            cls :'headerButtonsCls',
             listeners: {
                    click: function () {
                        new Ext.form.Panel({
                            width: 200,
                            height: 200,
                            title: 'Foo',
                            floating: true,
                            closable: false
                        }).show();
                    }
                }

    }

But the above code displays the panel in middle of the screen as a modal which i don't want (as i said i want it right under the header) So how to achieve that ? Thanks .

I took Muzaffers answer as base and added the feature to use the event coordinates here:

 var windowPanel = Ext.create('Ext.Panel', {
     bodyStyle: 'background: #ffff00;',
     border: true,
     height: 200,
     width: 200,
    floating:true
 });
 Ext.create('Ext.Container', {
     renderTo: Ext.getBody(),
     items: [{
             xtype: 'button',
             text: 'Show/Hide Panel',
             handler: function (btn, event) {
                 windowPanel.showAt(event.getXY())
             }
         }
     ]
 });

Here is the fiddle: https://fiddle.sencha.com/#fiddle/3a8j&view/editor