"growing" body parts on animals?

On a season 4 episode of Nip/Tuck, Rosie O'Donnell plays a woman who lost an ear in a vicious attack. They "grew " her a new ear on the back on a special mouse, I'm uming using stem cells. IS THIS REALLY POSSIBLE? I know scientists are working on cultivating organs out of other cells, but do they really GROW them on animals?