Heroin (diacetylmorphine or morphine diacetate), also known as diamorphine, and colloquially as H, smack, horse, brown, black, tar, and other names, is an opioid analgesic synthesized by C.R. Alder Wright in 1874 by adding two acetyl groups to the molecule morphine, found in the opium poppy. It is the 3,6-diacetyl ester of morphine, and functions as a morphine prodrug, meaning that it is metabolically converted to morphine inside the body in order for it to work.