Graphene sheet, electron interference spectroscopy. This image shows strong interference patterns generated by atomic scale defects in the graphene crystal (red areas) but smaller disturbances caused by larger scale bumps in the sheet (blue areas). The electron energy in graphene is inversely proportional to its wavelength. The area here, imaged at a voltage of 30 millivolts (mV), is around 40 nanometres square. This research was carried out at the Center for Nanoscale Science and Technology (CNST) of the National Institute of Standards and Technology (NIST). Image published in 2007.