Shinya Yamanaka: In my Ph.D. school, I didn’t work on stem cells.  I just worked on basic pharmacology.  But by doing pharmacology, I got very interested in so-called “knockout mouse” technology.  Knockout mouse is a way to study the function of genes. You know, both human and mouse have approximately 20,000 genes. With knockout mouse technology, we can select one gene out of those 20,000 genes, and completely destroy that one particular gene so that we can understand the function of that particular gene. I got very interested in that technology.  It was 1992 or 1993 when I graduated from my Ph.D. school. So I decided to study — I decided to learn about knockout mouse technology.  But at that time in Japan, only a few scientists were working on knockout mouse technology.  That’s why I decided to move to the States, San Francisco.