The institute “Fundamental physics for metrology” has been recently established at the PTB in order to advance the quantum theory of atomic and mesoscopic systems. The institute’s activities range from the high-precision analysis of atomic structure and collisions, to the description of coherent processes in ultra-cold quantum gases and phase transitions in magnetic systems. These research activities aim to support the development of new metrology standards, the precise determination of fundamental physical constants, and tests of fundamental symmetries of Nature.