The resolution of scanning tunnelling microscopes can be improved dramatically by attaching small molecules or atoms to their tip. The resulting images were the first to show the geometric structure of molecules and have generated a lot of interest among scientists over the last few years. Scientists from Forschungszentrum Jülich and the Academy of Sciences of the Czech Republic in Prague have now used computer simulations to gain deeper insights into the physics of these new imaging techniques. One of these techniques was presented in the journal Science by American scientists this spring. The results have now been published in the journal Physical Review Letters.