If you think stem cell research can polarise opinion, just wait for the reaction to this. In 2004, a fertility scientist named Panos Zavos claimed to have implanted a cloned embryo in a human uterus, but that it failed to create a pregnancy. The science world told him to shut up and publish his findings. And now, he has done, in an obscure but genuine science journal, along with claims that he has tried the procedure a number of times since. Let the frantic ethical battle commence.