Nat. Biotechnol. 35, 659–666 (2017); published online 31 May 2017; corrected after print 14 August 2018

In the HTML and PDF versions of this article initially published, μ's appeared as m's throughout the scale bar lengths in the figure legends, as well as in the Methods section in the phrases “added to give a final volume of 150 μl per well,” “an average hPSC cell size of 15 μm” and “sectioned on a vibratome to collect 300-μm sections.” In the HTML version, μ's appeared as m's in all instances throughout the Methods section except “35 μg/ml of pure laminin” and “35 μl laminin/entactin + 25 μl collagen.” The errors have been corrected in the HTML and PDF versions of the article.