Kenneth G. Libbrecht is a professor of physics and chairman of the Physics Department@the California Institute of Technology. He received his Ph.D. in 1984 from Princeton University. His research has spanned a wide range, from solar activity to gravitational waves, but his interests in crystal growth led him to study and photograph snowflakes. Some of his images, which can be seen@www.snowcrystals.com, were put on a series of stamps released by the U.S. Postal Service in October 2006. Libbrecht is the author of several books on snow crystals, most recently Ken Libbrecht's Field Guide to Snowflakes (Voyageur Press, 2006). Address: Physics Department, Caltech 264-33, Pasadena, CA 91125. Internet: kgl@caltech.edu