In Windows Phone 7 3D game programming, the models come from the modeling software, such as 3DS MAX or Maya, which are used frequently. Sometimes, it you do not want to control a complete animation, just part of it. At that moment, you should know the subdivisions where they are. Actually, the models are organized as a tree, and you can find a specified mesh or bone using a tree-based binary search algorithm; however, there is no need to write an algorithm, as the XNA framework has done them for you. As a handy reference, you should know the hierarchy of the model and the name of every part. In the recipe, you will learn how to get the model hierarchy information.