The original mission of TLK was the development of tritium technologies for the fuel cycle of fusion reactors. As a result of past R&D work TLK now has many similarities with the proposed ITER Tritium Plant. Because of its complete tritium infrastructure and its long lasting experience in tritium processing the TLK was chosen to host the Karlsruhe Tritium Neutrino experiment KATRIN. KATRIN will allow for model-independent measurements of the neutrino mass scale and thus should help to clarify the role of neutrinos in the early universe. The future of TLK is R&D ‘between fusion and cosmology’ based on its key competences, namely tritium technology and the closed tritium loop.