This chapter explored MDI programming and design. The chapter began with an introduction to .NET's effortless MDI features, and showed how to use menu merging, simple synchronization, and MDI layout styles. It continued in more detail with a sophisticated example of document-view architecture, which provides the freedom to create multiple synchronized views hosted in separate windows or the same window. Finally, the chapter ended by delving into one of MDI design's hottest topics with an introduction to coding your own dockable windows.