We are a theoretical biophysics group that has the good fortune to be part of a large department housing both experimentalists and theorists, the Department of Bionanoscience at the TU Delft. Our central research question is how many actors act together in the complex environment of living systems. We study systems ranging from single molecules such as proteins and molecular motors, all the way up to cells in tissues and colonies of bacteria. In particular, we are currently working on the effects of membrane mediated interactions, mechanical interactions between cells in developing embryos, and collective dynamics of finite-size, self-propelled particles. On all these, we cultivate active collaborations with theoretical and experimental groups, both inside and outside our own department.