Stem cells from a mouse embryo have been coaxed into producing both eggs and sperm in the same dish. The eggs and sperm are the most mature yet grown in the lab, and the advance brings researchers closer to their ultimate aim: producing human eggs and sperm from adult body cells so that infertile men and women can have their own children.
Applying the technique to humans would be controversial, not least because it raises the possibility that men might be able to produce eggs, and women sperm. But researchers point out that any human application would be decades away, which would allow time for ethical debate over the technology.
In the meantime, they hope that lab-produced eggs and sperm will help them to learn exactly how these cells are created in the body, something that is crucial to understanding fertility disorders and embryo development.