Matthew P. Walker earned his Ph.D. from the Medical Research Council in London in 1999. Following stints as a postdoctoral fellow and instructor in psychiatry and psychology@Harvard Medical School, he became an assistant professor of psychology in 2004. He is currently director of the Sleep and Neuroimaging Laboratory. Address: Sleep and Neuroimaging Laboratory, Department of Psychiatry, Beth Israel Deaconess Medical Center, Feldberg, FD 862, Harvard Medical School, Boston, MA 02115. Internet: mwalker@hms.harvard.edu