On Feb. 17th, 2020, in Aachen, there has been the Kick-off meeting of the Collaborative Research Center (CRC1394) that aim at building fundations of defect phase diagrams. This project funded for 4 years by the DFG (German Research Agency) gathered the strengths of 19 principal investigaors (PIs) from the RWTH Aachen, the Max-Planck Institut for Iron Research (MPIe, Düsseldorf) and the FAU Erlangen-Nurnberg.