Rainer spent several years as a postdoctoral researcher in the USA, Hungary, Belgium and Germany before moving to Queen Mary University of London in 2004 as a lecturer in applied mathematics. His research combines dynamical systems theory, nonequilibrium statistical physics and stochastic theory to understand complex systems, with applications to nanoscience and biology. He is interested in the emergence of fractal structures in chaotic transport processes such as diffusion. More recently he started to apply the theory of anomalous stochastic processes to understand the foraging of biological organisms; examples are stochastic models of biological cell migration and bumblebee flights. His research in theoretical physics and applied mathematics thus stretches from mathematical foundations to experimental applications. For three years he was Director of Postgraduate Research Studies at the School of Mathematical Sciences. For many years he was teaching large first year courses like Calculus, more recently he taught differential equations and dynamical systems theory.