A tobacco pipe, often called simply a pipe, is a device specifically made to smoke tobacco. It comprises a chamber (the bowl) for the tobacco from which a thin hollow stem (shank) emerges, ending in a mouthpiece (the bit). Pipes can range from very simple machine-made briar models to highly prized hand-made artisanal implements made by renowned pipemakers, which are often very expensive collector's items. Pipe smoking is the oldest known traditional form of tobacco smoking.