Nature Reviews Molecular Cell Biology 12, 643–655 (2011)

The authors wish to correct two typographical errors in the above article. On page 654, there was an error in the highlighted reference comment. The text “References 74–76 and 103 use groundbreaking imaging technology to visualize HSCs in the niche in mice. The authors of references 74, 75 and 103 image murine bones ex vivo, and the authors of references 75 and 76 image cells in the bone in vivo.” should have read “References 74–76 and 103 use groundbreaking imaging technology to visualize HSCs in the niche in mice. The authors of references 74 and 103 image bones ex vivo, and the authors of references 75 and 76 image cells in the bone in vivo.” Also, on page 650, 'TPO' should have been 'THPO' in figure 5 and 'TPO, thyroid peroxidase' should have read 'THPO, thrombopoietin' in the legend. The Online version has been corrected, and the authors regret any confusion caused to the readers.