Popup offers many advanced features beyond simply adding small overlays of arbitrary content. These features are listed below:

• Create popovers and dialogs
  The Popup control enables you to add small overlays of arbitrary content to your applications, as popovers or modal dialogs. Popovers have owner elements to control their visibility whereas dialogs are the pop ups with no owner elements. Hence, a popup behaves like a popover when the element that owns the popup is specified by the Owner property, otherwise, it behaves like a dialog.
  
  
• Manage popup display
  You can control the actions that show the popup using the ShowTrigger property. By default, this property causes the popup to appear when user clicks the owner element. If it is set to None, the popup can only be shown when the show method is called.
  
  
• Alerts and prompts
  The Popup control can be used to implement static methods for showing alert and prompt dialogs.
  
  
• Transition effects
  You can animate the popup when it is shown or hidden using the FadeIn and FadeOut properties of the Popup class.
  
  
• Resizable dialogs
  Popup allows you to determine whether the popup can be resized by dragging its edges with the mouse using the IsResizable property. In addition, you can limit the size of the popup using the CSS properties.