This talk will focus on some of the molecular aspects of psychedelics acting at the serotonin 5-HT2A receptor, with an emphasis on LSD and certain of its congeners. Restraints within the binding site of the serotonin 5-HT2A receptor force the diethylamide of LSD to adopt a specific conformation, which was initially proposed by the author in 2002. A recent x-ray crystal structure of LSD bound within the serotonin 5-HT2B receptor has given a molecular picture of LSD binding, and has further elucidated the basis for the importance of the diethylamide moiety. In addition, receptor kinetics studies of LSD have shown that equilibration of LSD in the receptor requires a long time, and once bound in the receptor, LSD leaves only very slowly. In addition, the long receptor occupancy of LSD is likely responsible for the fact that its intracellular signaling is biased toward beta-arrestin2.