Nature Communications 3: Article number: 763 (2012); Published: 27 March 2012; Updated: 21 May 2013.

In Fig. 1 of this Article, two image attributions were inadvertently omitted. The image of graphene that appears in each panel of the figure was reproduced with permission from James Hedberg (www.jameshedberg.com). The tooth image in Fig. 1b was reproduced courtesy of Georgianax/ Vecteezy.com.