Complexity research focuses on the analysis and empirical validation of models based on “bounded” rationality of agents. The behavior of these agents is in accordance with experimental and empirical evidence rather than standard assumptions on rationality. The central question is which aggregate behavior results from interactions of individual decisions of boundedly rational agents? Research topics are: complex systems & nonlinear dynamics; bounded rationality, learning & heterogeneous expectations; behavioral & experimental macro-finance; networks; dynamic games; strategic interaction and (non-)cooperative games.