LSD (lysergic acid diethylamide), first synthesized in 1938, is an extremely potent hallucinogen. It is synthetically made from lysergic acid, which is found in ergot, a fungus that grows on rye and other grains. It is so potent its doses tend to be in the microgram (mcg) range. It's effects, often called a "trip", can be stimulating, pleasurable, and mind-altering or it can lead to an unpleasant, sometimes terrifying experience called a "bad trip."