Tsien, Roger Yonchien, 1952–, American biochemist, b. New York City, Ph.D. Cambridge, 1977. Tsien was a researcher at Cambridge (1977–81) and a professor at the Univ. of California, Berkeley (1982–89). He has been a professor at the Univ. of California, San Diego, and an investigator of the Howard Hughes Medical Institute since 1989. Tsien shared the 2008 Nobel Prize in Chemistry with Martin Chalfie and Osamu Shimomura for the discovery and development of green fluorescent protein (GFP), which is now used to identify and track specific proteins in living organisms. Tsien furthered the general understanding of how GFP fluoresces, and he extended the color palette beyond green, allowing researchers to assign various proteins and cells different colors so that several different biological processes can be followed simultaneously. As a result of his and his co-recipients' work, GFP has become one of the most important tools in contemporary bioscience.