At first glance, magnetite appears to be a rather inconspicuous grey mineral. But on an atomic scale, it has remarkable properties: on magnetite, single metal atoms are held in place, or they can be made to move across the surface. Sometimes several metal atoms on magnetite form small clusters. Such phenomena can dramatically change the chemical activity of the material. Atomic processes on the magnetite surface determine how well certain metal atoms can serve as catalysts for chemical reactions.Scientists at TU Wien (Vienna), together with colleagues from Utrecht University, can now watch single platinum atoms form tiny clusters. Carbon monoxide plays a dual role in this process: It allows single platinum atoms to move and form pairs, and then it holds these pairs together for a long time. Only by increasing the temperature can the pair-bonds between platinum atoms can be broken.