Abstract: The recent progress in fundamental study of friction, including molecular dynamics simulation of superlubricity, interfacial friction testing, commensurate theory on the origin of friction, and the investigation of energy dissipation during friction process, is reviewed. It is true that the simulation of superlubricity and its theoretical explanation are inspiring to promote the fundamental study and practical control of friction, but the difference between computed results and the physical reality deserves a further investigation. It is the difference that encourages us to go beyond the classical mechanics and to explore at depth the unknown world of friction.