The introduction of the tranquilizer chlorpromazine (also known as thorazine) in the 1950s represented a turning point in psychiatry, one that gave rise to the “psychopharmacological revolution.” Indeed, not only was chlorpromazine successful—by 1964 some 50 million people had taken the drug—but its development also laid the groundwork for the later generation of agents used in the treatment of anxiety and depression. Furthermore, the characterization of its effects on neurotransmitters and their receptors provided insight into how impulses are passed from one neuron to the next in the brain, leading to major advances in scientists’ understanding of mental illness and cognition.