NEW YORK (AP) Scientists say they've grown human cells inside pig embryos, a very early step toward the goal of growing livers and other human organs inside animals to transplant into people.
The cells made up just a tiny part of each embryo, and producing any organs this way is far in the future.
Pigs might be useful in part because they are big enough to make human-sized organs. In the new study, reported Thursday, the embryos were grown for only a few weeks.
The scientists are working toward making pancreases, hearts and livers in pigs.
Such human-animal experiments have raised ethical concerns.