Researchers in Japan are progressing in vitro gametogenesis (IVG), a field of biomedical research aimed at creating unlimited supplies of “artificial” eggs and sperm from any cell in the human body. About the technique: IVG involves reprogramming cells from a person’s blood or skin into induced pluripotent stem cells, which can theoretically become any cell in the body, including egg and sperm cells. Technical challenges: Katsuhiko Hayashi, a developmental geneticist at Osaka University in Japan, is a pioneer in the field of IVG.