The lifetime of Solid Oxide Fuel Cell Stacks was investigated by means of experimental investigations (e.g. Impedance spectroscopy, physical/electrochemical characterization), microstructure analysis (SEM, FIB-tomography, EDX) and numerical simulation (Finite Element Modelling).A particular focus of the investigations was on the effect of microstructure degradation of Ni-based cermet anodes (e.g. Ni-coarsening) in context with temperature variations and redox cycling. Quantitative relationships between microstructure characteristics (phase volume fractions, tortuosity, constrictivity) and effective properties (electric and ionic conductivity, gas diffusivity) could be elaborated. Based on the fundamental understanding of microstructure-property relationships new anodes with improved long-term performance could be developed.