Korean scientists on Thursday confirmed that they lead the world in research to use human cloning to repair damage caused by disease and injury. Hwang Woo-suk’s team at Seoul National University has cloned embryos from 31 people with inherited diseases or spinal injuries – and cultivated embryonic stem cells from 11 of these.

The study, published online by Science, the US journal, shows the researchers have made “astonishing progress” in refining their technique over the past year, says Gerald Schatten of the University of Pittsburgh, who advised them on data analysis and presentation.