Some hallucinogens appear in nature, such as psilocybin (magic mushrooms) and mescaline (peyote), and have been used throughout history to generate visions or mystical insights. Chemically synthesized hallucinogens include ketamine, PCP (phencyclidine or angel dust), dizocilpine, LSD (lysergic acid diethylamide), and MDMA (also known as ecstasy or Molly).