Mining the secrets of the egg

Less than a month ago, investigators at Seoul National University in South Korea announced that cloning researcher Woo Suk Hwang had lied when he claimed his team cloned human embryos with relative ease and produced stem cells from them. The news was a significant setback for cloning researchers. In this special section, Nature looks at how biologists are regrouping. Carina Dennis asks how they can get cloning to work given a very limited supply of eggs and Phyllida Brown looks at whether we will need therapeutic cloning at all, if immunologists can stop our bodies fighting transplants (see page 655). And on page 658, one of Hwang's closest rivals admits it may not continue its cloning quest.J. KING-HOLMES/SPL[graphic not available: see fulltext]