Electron microscopy has been used to image nanocontacts. Panels (a) and (b) show the spontaneous welding of a gold nanojunction. Images reproduced with permission from Merkle and Marks [78]. Copyright 2008 by Elsevier. Panel (c) shows a separate gold nanobridge, prior to failure in tension. Image reproduced with permission from Rodrigues et al. [79]. Copyright 2000 by American Physical Society. Panel (d) shows a dissimilar nanocontact (Pt/Ir on W) that does not spontaneously weld but instead the original interface remains distinct. Image reproduced with permission from Alsem et al. [80]. Copyright 2016 by Cambridge University Press.