Timothy Leary nearly killed the psychedelic revolution. He did more than anyone to popularize LSD and urged us all to "turn on, tune in, drop out." But Leary's indiscriminate use of mind-altering drugs created a backlash, and made them taboo for serious scholars. Now a new generation of scientists is studying hallucinogens, and finding remarkable effects. In this hour, we'll take you to the cutting edge of psychedelic research.