Heroin, chemically known as diacetylmorphine, is an illegal drug synthesized from morphine, a naturally occurring substance extracted from the seed pods of certain varieties of poppy plants. It was initially created to serve as a less addictive alternative to morphine but quickly proved to be even more addictive and dangerous. In the United States, heroin is classified as a Schedule I controlled substance, which is meant to include drugs with a high potential for abuse and has no accepted medical use.