Nat. Med. 17, 1344–1346 (2011); published online 7 November 2011; corrected after print 7 November 2011
In the version of this article initially published in print, the figure had incorrectly shown the receptor on the osteoclast progenitor as RANKL and the corresponding ligand on the osteoblast as RANK, instead of RANK on the osteoclast progenitor and RANKL on the osteoblast. The figure labeling was always correct in the HTML and PDF versions of the article.