Psychedelics (also known as serotonergic hallucinogens) are a class of psychoactive substances that produce an altered state of consciousness marked by unusual changes in perception, mood, and cognitive processes.
Psychedelics can be divided into three major sub-classes: tryptamines, lysergamides, and phenethylamines. Psychedelic tryptamines are based on, or derive from, dimethyltryptamine (DMT), lyergamides on LSD, and phenethylamines on mescaline.