Marijuana is the slang term for portions of the Cannabis plant. It is one of the oldest psychoactive substances used by man.
Marijuana, also called pot, weed, ganja, mary jane, and a host of other nicknames, is made from the Cannabis plant, which has three species: Cannabis sativa; Cannabis indica and Cannabis ruderalis. The flowering plant, which can grow to 16 feet (5 meters) high, likely originated in the Central Asian steppe, near the Altai or Tian Shian Mountains, and was first cultivated in China and India, according to "Cannabis and Cannabinoids: Pharmacology, Toxicology and Therapeutic Potential," (Routledge, 2002).