A team of Israeli researchers transplanted human and pig kidney stem cells into mice, where they developed into small kidneys that appear to work.

Stem cells are parts of a developing embryo that can change into various organs as the baby grows. Harvesting stem cells causes the death of the embryo, which has made the process a focus of controversy.

 But in work at the Weizman Institute of Science in Israel, the researchers used cells from  aborted embroyos, not live embryos grown for that use. The cells destined to become human and pig kidneys were transplaned into mice by a team led by Yair Reisner.