Ethical qualms moved Japanese scientist Shinya Yamanaka to work on reprogramming, his stunning recent breakthrough in stem cell research. In an interview with the New York Times, Dr Yamanaka remembers a day eight years ago when he paid a social visit to a friend's IVF clinic. He peered through a microscope. "When I saw the embryo, I suddenly realised there was such a small difference between it and my daughters," said Dr. Yamanaka, 45, a father of two and now a professor at Kyoto University. "I thought, we can’t keep destroying embryos for our research. There must be another way."

That epiphany inspired him to search for alternatives to embryonic stem cell research, which is restricted in both Japan and the US. Even in his laboratory in Kyoto he is not permitted to use human embryos. He has another small lab at the University of California, San Francisco, where he uses human embryos to verify that his reprogrammed cells are truly the equivalent of embryonic stem cells. He says that he has never handled human embryonic stem cells himself. Nonetheless, Dr Yamanaka still insists that the door should be left open to embryo research. "There is no way now to get around some use of embryos," he says. "But my goal is to avoid using them." ~ New York Times, Dec 11