On 2 July 2000, a small black piglet was delivered by a white sow. Xena's dark color was a clue that she was not the warrior princess whose name she bears but the product of the first successful pig cloning from fetal cells. As reported in the 18 August Science, this cloning adds to reports of cloned sheep, cattle, and goats (Onishi et al, Science 2000, 289:1188-1190). Xena was produced using a technique developed in mice in which a nucleus from a somatic cell is microinjected into an enucleated oocyte. This technique contrasts with the cell-fusion method used to produce Dolly the sheep. It took the transfer of 110 embryos to produce one live cloned piglet. But if the process can be made more efficient, Xena's creators hope to use cloning to propagate pigs with good growth characteristics, and to make genetic changes that will allow pig...