We conceive this birthday contribution as an eye-opener and an introduction to a new sub-discipline of Computer Science, model science and practice—modelology. It actually represents the fourth dimension of Computer Science, but it is so fundamental that all other dimensions must refer to it. A sub-discipline can only be effective if it is also practical and workable. Therefore we have to understand modelology not as representation science or even as a drawing tool for the visualization of complicated things, but as a broadly everywhere applicable systematic science and practice of modeling. Models should not only facilitate understanding but above all accompany system development and perfection.