In the article “Simple switch turns cells embryonic”, Nature 447, 618–619; doi:10.1038/447618a 2007 Shinya Yamanaka is quoted as saying he has not worked with embryos before. In fact, Yamanaka used fibroblasts derived from mouse embryos for the experiments described. In other experiments outlined in the article, the same results were achieved with fibroblasts taken from postnatal skin cells.