Complexity in pipe tobacco occurs several ways. There are blends that have five or six, and sometimes more, different tobaccos. These don't always work well, but when they do, you get a kind of orchestrated flavor when different flavors come forward in sequence and in combination. This usually only works with non-aromatics, since non-tobacco flavorings block some tobacco flavors. Complexity can also occur with two or three different kinds of leaf, or for that matter in single-leaf tobacco if it is of high quality. In general, the more kinds of leaf in a blend, the better it is to have a broad bowl pipe to allow the various tobaccos to burn at once. With single leaf, I find a medium diameter bowl with more depth works well. Complexity isn't always required. Some excellent blends have a simple, mellow taste that is extremely satisfying.