In recent decades, simulation-driven development has increasingly become established as a central method in industry and academia. Classically, systems are modelled in a single tool, which is referred to as monolithic approaches. With the increased complexity of systems and the need for linking several domains in one model, monolithic approaches have restrictions. Ideally, every subsystem is modelled in a tool that meets the particular requirements for the domain and the structure of the model. Thus, the need for coupling different tools is a pragmatic one. Co-simulation is an approach to enable a simulation of complex single or multi-domain systems that consists at least two subsystems (modelled in different tools) which solve coupled (algebraic) differential systems of equations . We present an overview of co-simulation, research challenges and opportunities based on an empirical survey.