Psilocybin is a chemical substance. It can cause hallucinations when eaten, and has also been found to reverse psychological conditioning, grow brain cells and heal the brain. It occurs in many kinds of fungi and mushrooms, most notably Psilocybin mushrooms. Most of these are known as psychedelic mushrooms. It grows in Europe, South America, Mexico, and the United States. Mushrooms that contain psilocybin are known as magic mushrooms.