SimulationX is a graphically-interactive tool for the holistic modeling, simulation and analysis of multi-domain systems from 1D to 3D. Multi-level customizing options and SimulationX’s capability to adjust the model’s complexity by mouse-click allow modeling in every step of the design process. Ready-to-use model libraries, e.g., for mechanics, multi-body systems, power transmission, hydraulics, pneumatics, thermodynamics, and electric drives are written in Modelica language. Libraries are extendable by Modelica-based modeling using the SimulationX TypeDesigner. A comprehensive API supports the integration into any CAE, CFD, CAD or database tool environment. Versatile interfaces offer plenty of opportunities for exporting models in terms of Simulink S-function and C-Code for HiL, RCP and other real-time applications. Different features (tracing, performance analyzer, switchable model complexity) support users in achieving real-time-capabilities.