Enlarge ImageMiraculous birth. A Chinese group isolated stem cells from mouse ovaries, transplanted them into sterilized mice, and got these normal babies. Credit: Kang Zou et al., Nature Cell Biology Advance Online Publication (12 April 2009) A new study challenges the long-held belief that female mammals start life with a limited number of eggs and cannot produce new ones after birth. For the first time, a Chinese group has found mouse cells that produce new eggs when transplanted into sterilized mice and give rise to normal offspring. The findings are already inflaming the debate over when and how female...