FOR AN END USER, THE MOST OBVIOUS THING ABOUT AJAX IS ITS VISUAL APPEARANCE. AJAX APPS TEND to look richer, and the interface tends to update smoothly, more like a desktop app than a conventional web app. This chapter describes the two main technologies for updating the user interface. Display Morphing focuses on changes to a single element, while Page Rearrangement involves changes to the page structure. Along the way, we'll look at the Document Object Model (DOM). DOM manipulation is key to many of the Ajax Patterns.