Heroin, chemical formula C21H23NO5, is a drug that is created from extracts of the opium poppy plant. An imitator of endorphins, heroin is known to create a sense of euphoria and well-being a short time after being introduced into the bloodstream. Heroin has an extremely high potential for addiction, and tolerance can occur quickly. Although illegal in the United States, heroin is a legal prescription in other countries under the name diamorphine. In its natural form, heroin usually exists as a brown or white powder. Popular street names for heroin include H, brown sugar, horse, black tar, Harry, Bobby, smack, junk, dope, moop, sweet lady, Halloween, B, Ghetto D, honk, diesel, gear, skag, Jenny, brown, ice cube, jim nix, big time, and calipop.