Psychedelics (hallucinogens) have remained of high interest for many decades due to their ability to produce unique and dramatic alterations in consciousness. Before they had been pharmacologically classified as 5-HT2A receptor agonists or partial agonists, psychedelic drugs like mescaline, psilocybin, and LSD, were recognized for their powerful effects on the human psyche. They produce such profound effects on perception that it is natural to ask how they work in the brain. What are their biological targets? Where are these targets located in the brain? Are those brain areas recognized to play key roles in perception and cognition? Further, as recent clinical research studies have begun attempts to unravel the basis for human consciousness, it has become apparent that psychedelics offer unique and powerful tools to help to elucidate the basis of consciousness. The age-old questions of who we are and why we are here seem inevitably to arise when people talk about their experiences with psychedelic drugs. Yet, this fascinating class of mind-altering substances has not received significant research attention for more than 50 years, and it is only within the past decade or so that they have been the subject of renewed research interest. A comprehensive review on psychedelics has recently appeared (Nichols 2016).