Engineering software and software intensive systems has become increasingly complex over the last decades. In the ongoing digitalization of all aspects of our lives in almost every domain, including, e.g., mechanical engineering, electrical engineering, medicine, entertainment, or jurisdiction, software is not only used to enable low-level controls of machines, but also to understand system conditions and optimizations potentials.To remain in control of all these heterogeneous systems of systems, a precise, but abstract understanding of these systems is necessary. To this end, models in their various forms are an important prerequisite to gain this understanding.In this article, we summarize research activities focusing on the development and use of models in software and systems engineering. This research has been carried out by the working group of Bernhard Rumpe, which started 25 years ago in Munich, continued in Braunschweig, and since 10 years carries on at RWTH Aachen University.