The seamless integration of large amounts of data into complex computer models is one of the great challenges of the mathematical sciences. The field of data assimilation has been advanced by applications in meteorology, hydrology, and resource retrieval. New applications in biology, medicine, and cognitive and neuroscience require novel assimilation techniques. Collaborative Research Center 1294 aims to systematically develop methods for data assimilation and demonstrate their efficiency using established and new application areas as examples.