Tobacco is a product prepared from the leaves of the tobacco plant by curing them. The plant is part of the genus "Nicotiana" and of the Solanaceae (nightshade) family. It is used as a drug, mostly by inhaling the smoke of, but also by using snuff or chewing. People use cigarettes, cigars, and pipe to make tobacco smoke. Tobacco contains the chemical nicotine, which causes pleasure as a stimulant drug. It also causes addiction — after people start using nicotine, it is difficult to stop. Tobacco use can cause diseases, such as many types of cancer.