Charles A. Czeisler, PhD, MD co-founded and directs the Division of Sleep Medicine at Harvard Medical School, where he is the Frank Baldino, Jr, PhD Professor of Sleep Medicine and Professor of Medicine. Dr. Czeisler is an elected member of the National Academy of Medicine and the International Academy of Astronautics and was awarded Honorary Fellowships by the Royal College of Physicians (London) and the American Physiological Society. He teaches undergraduate courses at Harvard College and is founding Chief of the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital. Dr. Czeisler discovered that retinal light exposure resets the brain’s circadian clock in humans, even in some totally blind people, and that light can be used to effectively treat maladaptation to night shift work; discovered that the brain’s circadian clock regulates sleep duration and structure; and has applied his research to improve shift work schedules. He characterized fundamental properties of the central circadian pacemaker(s) in humans, including their entrained phase, intrinsic period and resetting capacity; discovered that exogenous melatonin administration can improve misaligned sleep; demonstrated that physicians’ extended-duration work shifts adversely affect both patient and physician safety; and designed the clinical trials that led to all three FDA-approved treatments for Circadian Rhythm Sleep-Wake Disorders. Dr. Czeisler led NASA’s Sleep Team, recording the sleep of astronauts during spaceflight; with his colleagues, he received NASA’s Innovation Award for designing the solid-state lighting system for the International Space Station to improve the sleep of astronauts. Dr. Czeisler has served on the Faculty of the World Economic Forum (Davos) and at Aspen Ideas Festival and Aspen Health and has served as President of the Sleep Research Society, Board Chair of the National Sleep Foundation, Chair of the NIH Sleep Disorders Research Advisory Board and is currently President-elect of the International Association of the Circadian Health Clinics. Dr. Czeisler has received the Lifetime Achievement Award from the National Sleep Foundation, the William C. Dement Academic Achievement Award and the Mark O. Hatfield Public Policy Award from the American Academy of Sleep Medicine, the NIOSH Director’s Award for Scientific Leadership in Occupational Safety and Health, the Lord Adrian Gold Medal from the Royal Society of Medicine (UK), the Mary Carskadon Outstanding Educator Award and Distinguished Scientist Award from the Sleep Research Society, the Green Cross for Safety Innovation Award from the National Safety Council, the Peter C. Farrell Prize in Sleep Medicine, Harvard Medical School Division of Sleep Medicine, and the J.E. Wallace Sterling Lifetime Achievement Award in Medicine from the Stanford University School of Medicine.