When you create a new drawing in Visio 2007, the wizard ask you to pick some pre-defined drawing type. These types include things like WorkFlow, Engineering etc. Depending on type of project you are working on, you can pick a template type. Based on your selection, you are presented with set of shapes in left view that you can use to create your drawing. But some time your drawing requires you to use shapes that may not be there in your pre-defined set. Those shapes may be present in some other shape types templates. For example while working on a drawing to create a data flow diagram for a line of business, I needed to include some shapes from Network > Web Diagram template. Choice of an initial drawing type does not limit you from choosing shapes from other project types. You can simply go to File > Shapes menu and select the type of shapes you want, and select it. Those shapes will now appear in left view of your document window.