Charles Czeisler  Charles A. Czeisler (born 1952) is an American physician and sleep researcher. He is a researcher and author in the fields of both circadian rhythms and sleep medicine. Czeisler graduated from Harvard College, "magna cum laude" in 1974, with a degree in Biochemistry and Molecular Biology. He received his Ph.D. in Neuro- and Bio-behavioral Sciences and his M.D. from Stanford University. His undergraduate thesis was focused on cortisol timing release. As a graduate student at Stanford, Czeisler continued his research in Dr. William Dement's lab. Elliot Weitzman, who both worked with and mentored Czeisler, influenced Czeisler to study sleep. Today, Czeisler is the Baldino Professor of Sleep Medicine and Director of the Division of Sleep Medicine at Harvard Medical School. Additionally, he works as the Division Chief of Sleep Medicine at Brigham and Women’s Hospital in Boston, Massachusetts. Czeisler has spent over 40 years researching the relationship between human sleep and the physiology of the human circadian clock and teaching a course at Harvard College on Circadian Biology for undergraduate and graduate students. In addition to his work at Harvard Medical School and Brigham and Women's Hospital, Czeisler is a Diplomate of the American Board of Sleep Medicine, an elected member of the Institute of Medicine, the International Academy of Astronautics and the American Clinical and Climatological Association, and a Fellow of the Royal College of Physicians, American Society for Clinical Investigation, and Association of American Physicians. Czeisler was one of Tibor Czeisler and Wanda Victoria Murzyn's three children. In 1993, Czeisler married Theresa Lynn Shanahan M.D. They now have three children and live in the Boston area. In his free time, Czeisler enjoys swimming, playing pickleball, and slalom waterskiing. Czeisler’s research focus is the neurobiology of human circadian rhythm. He examines the relationship between the circadian oscillator and sleep homeostasis, and how this interaction affects health. Czeisler's research interests encompass many areas including body temperature rhythms  and the effects of melatonin on humans (2011). Czeisler investigates how the physiological system works to reset the circadian pacemaker. His team discovered that light transduced by non-visual input (melanopsin activation) could reset the circadian clock in patients without sight.