The Theoretical Spectroscopy group develops theoretical and numerical approaches for the calculation of electronic properties, in particular many-body effects in electronic spectra. The research profile of the group has been defined in 2000; it is centred on the theoretical description of electronic excitations from first principles. The global aim is to design techniques which can be applied to a wide range of systems, from small clusters to bulk materials, from metals to insulators. These developments comprise a part of fundamental theory, the design of approximations, the implementation of the new theory in ab initio computer codes, testing and benchmarking of the results, and applications to interesting materials. Applications often combine fundamental questions and technological interest, examples being materials for data storage, for solar energy production or optoelectronics.