Hallucinogens are the mind altering drugs. These drugs changes the thinking, perception, consciousness and emotions. On consumption of these drugs can make things see, smell, hear and taste that are unrealistic. These can be categorized as psychedelics, which are the drugs responsible for changing the way how the human being perceives the world.
Examples of hallucinogens
LSD (lysergic acid diethylamide)
Mescaline (peyote cactus)