Psilocybin is a chemical found in over 100 species of mushrooms worldwide, it is converted to Psilocin in the body and it is Psilocin which causes sensory alterations commonly referred to as hallucinations. Psilocybin and Psilocin have a similar structure to serotonin and so have a high affinity for serotonin receptors in the brain. Psilocybin is converted to Psilocin in the body and it is Psilocin which causes sensory alterations commonly referred to as hallucinations. 

Psilocybin containing mushrooms are found in the wild or can be cultivated, the strength of the mushrooms can vary greatly but cultivated mushrooms are more likely to be stronger.

Typical onset of hallucinogenic effects of Psilocybin is usually within 20 to 40 minutes of use and can last up to 3-6 hours, with a threshold for intoxication of approximately 40 mcg/kg of body weight.