Lattice of copper atoms, coloured scanning tunelling micrograph (STM). This image was produced by a custom-made scanning tunnelling microscope at the US National Institute of Standards and Technology (NIST). The tip of the STM drags a cobalt atom across a closely packed lattice of copper atoms. The large rounded area are where the cobalt atom bonds to the copper atoms at its preferred, lowest energy bonding site. The bright triangle-shaped areas are where the atoms bond at a higher energy site. Dark areas show positions that the cobalt atom hops over, refusing to bond to at all. Image published in 2007.