Albert Hofmann referred to lysergic acid diethylamide, better known as LSD, as his "problem child." The wonderful but worrisome psychedelic drug discovered by Hofmann both inspired and unsettled the world, with the mischief of Timothy Leary, the "acid tests" of the Merry Pranksters, and social experiments during the Summer of Love and Woodstock--two events that altered popular music--capturing headlines in the 1960s. This second edition encyclopedia updates and adds more than 200 new entries, from Hank Williams III and Tucker Carlson to dinosaurs. New entries provide documentation of LSD's influence during the 1960s and address a recent resurgence of cultural relevance for the drug.