Nat. Biotechnol. 26, 215–224 (2008); published online 3 February 2008; corrected after print 26 February 2008

In the version of this article initially published, the author name Akiori Akaike should have been Akinori Akaike, and the density of ES cells and the composition of RA/T medium are incorrect. The errors have been corrected in the HTML and PDF versions of the article.