The computer of our day-to-day environments offer a plethora of interaction techniques. The shift from interacting with dedicated “computers” to interacting with distributed ensembles of computational devices (so-called pervasive computing environments, PCE) will fundamentally change our understanding of interacting with a “system” in which almost any action turns into “operating a computer.” The overarching research question of the Priority Programme is to understand the nature of interaction with large and complex pervasive computing environments and to explore suitable interaction paradigms.