Using eggs from young donors to repair the damaged eggs of older women who hope to conceive, researchers are one step closer to creating a baby that, biologically speaking, has three parents. While they haven’t yet used these eggs to produce babies, they have been injected with sperm to produce an early embryo in the lab. The technique could be used to increase the chances of fertilization for older women, or to reduce the chance of genetic illness, but it’s also likely to provoke outrage among critics who say it could lead to genetically modified children. In vitro fertilization often fails in older women because of abnormalities on the outside of their eggs. But the team of researchers at St. Mother Hospital in Japan think they could implant the healthy nucleus, containing most of the information needed to produce a baby, into the cytoplasm of a young mother donor. They did this successfully in 31 eggs; of these, seven formed “early stage embryos” when injected with sperm in a test tube.