Katsuhiko Hayashi pulls a clear plastic dish from an incubator and slides it under a microscope. "You really want to see the actual cells, right?" Hayashi asks as he motions toward the microscope.

In-vitro gametogenesis, or IVG, is a concept that sounds like science fiction but is slowly becoming a real possibility. Imagine creating eggs or sperm from skin cells, all outside the body. It’s a ...