A complex fluid consists of (a large number of) similar mobile entities which are complex enough by themselves to preclude a straightforward prediction of the collective behaviour of the whole. Our research aims at understanding emergent phenomena in complex fluids, in particular in active fluids. We hope to identify suitable model systems which yield insight into overarching principles of self-organization in systems as diverse as granular flows, swarming of plankton particles, or patterns in traffic flow. One challenging question is: are there general common ‘principles’ behind the various instances of symmetry breaking, structure formation, and emergence in open systems? How does nature proceed from ‘being’ to ‘becoming’?