Theory is one of the most important bridges between all fields covered by MAINZ. Close interaction between theory and the corresponding experimental groups is the basis of the success of MAINZ. The unique feature of this area is a strong emphasis on computer simulation methods. These methods aim at providing detailed predictions of properties and functionalities of specific compounds, and at combining different theoretical and numerical techniques to obtain a complete description. Here, we build on a long-standing tradition in developing coarse-graining and multiscale simulation techniques for materials science. Rational design using theoretical input was successfully demonstrated in case of new materials (topological insulators), and interfaces and devices. In future, we will focus on hybrid simulation methods for materials science, e.g., methods combining molecular and continuum descriptions of materials or mixed quantum/classical descriptions.