This comprehensive review examines how scientists use advanced imaging techniques like PET and SPECT scans to study how hallucinogenic drugs such as LSD and psilocybin interact with the brain. The research shows these drugs primarily bind to serotonin receptors, particularly the 5-HT2A subtype, which appear responsible for producing hallucinations. While scientific understanding of hallucinogen mechanisms has advanced significantly, there is still much to learn about their complete effects on brain chemistry and their potential therapeutic applications.