• energy dissipation;
  • friction force microscopy;
  • nanotribology;
  • superlubricity;
  • thermolubricity

The field of friction is usually associated with its obvious practical importance. This tends to emphasize the engineering aspects of friction and thereby hides the fact that there is a wealth of interesting physics involved, part of which cannot be regarded as fully understood at present. New techniques, such as friction force microscopy, have started to provide access to the phenomenon of friction on the atomic scale. This has given a strong impulse to the field of tribology, pushing it significantly beyond the engineering level and into the regime of the fundamental aspects of frictional energy dissipation. This article reflects the authors’ personal view on matters of interest in the field of atomic-scale friction. Rather than to review important contributions in this field, we have chosen to summarize what has been learned and identify phenomena that may seem familiar to tribologists but actually should be regarded as non-trivial from a physical point of view.