This chapter describes the Demonstrator Platform (DP), a framework for simulation of devices, interconnects, circuits, electromagnetic fields, and thermal effects. This framework is used to develop and test new mathematical methods and algorithms. Section 8.1 describes the design of the DP and gives an overview of the available modules. Section 8.2 is a tutorial on how to use the DP focusing on model-order reduction. It shows for the example of a micro-hotplate model all the steps needed to apply model-order reduction, including postprocessing and error estimation. In a second part, a coupled simulation of a circuit combined with a reduced model of a transmission line is presented. Section 8.3 emphasizes the aspect of the DP as a development framework. After introducing the benchmark example of an n-channel power MOS-FET, it is shown how to combine and extend different modules of the DP to a fully coupled electro-thermal simulation of the device