Our objective for the volume has been to summarize the current state-of-the-art of psychedelics research. As editors, we faced the seemingly impossible task of distilling the entire breadth and depth of this rapidly expanding field into a single volume. It proved difficult to narrow the scope down to a reasonable level. We selected topics that span a wide range of areas, including pharmacological interactions occurring at the molecular level, changes in signaling pathways, effects on individual neurons and neural networks, and reaching all the way up to the level of the whole brain and the mind. We believe the 14 peer-reviewed chapters that were selected for inclusion provide up-to-date information about the pharmacology, neurobiological effects, subjective experience, and therapeutic effects of psychedelic drugs.