Susumu Tonegawa’s father and uncle were engineers and scientists, which was probably the initial influence in his deciding to pursue a career in science. By his senior year in college, fueled by the cornerstone papers by François Jacob and Jacques Monod of the Pasteur Institute, his interests were turning toward the nascent field of molecular biology. Molecular biology was just emerging as a discipline, and the lab of Professor Itaru Watanabe at the Institute for Virus Research at Kyoto University was one of Japan’s earliest pioneers in the field. However, Professor Watanabe encouraged Susumu to apply to UCSD, which was just being established. Professor Watanabe spoke with David Bonner, the head of the new Department of Biology there, and arranged for Susumu to attend the graduate school. At that point, Susumu knew nothing about the brain or prokaryotic molecular biology, but began by studying the field in the laboratory of Professor Masaki Hayashi. He then moved to the Salk Institute for 2 years, to the lab of Renato Dulbecco, who was to have a profound influence on his life. Professor Dulbecco was an expert in tumor virology, and Susumu wanted to study more complex systems with a focus on eukaryotic molecular biology…