Nat. Immunol. 17, 18–25 (2016); published online 17 December 2015; corrected after print 24 October 2016
In the version of this article initially published, the citation of Figure 3 in the second paragraph of the third subsection (Chromatin: the nexus of phenotype and the environment) is incorrect. That should cite Figure 2, as follows: “From an evolutionary perspective, two extreme models of how such complexity might be generated and regulated can be envisaged95 (Fig. 2).” The error has been corrected in the HTML and PDF versions of the article.