Simple Systems have few components and their behavior is in all respects fully understandable and predictable. An example would be a solid ball falling under the action of gravity through air. This Simple System consists of the ball, the air, and the gravitational force. Here we usually assume a single ball, constant acceleration of gravity, a viscous drag on the ball, and Newton’s laws. When making these assumptions, we arrive at very useful answers. We did, however, neglect many aspects. If, for example, we would ask how the behavior changes when we go from one ball, to two, to three, or even more balls that fall close to each other, our “Simple System” assumption fails. It is not sufficient to generalize from one ball’s behavior to many. Instead we need to consider the interaction of the balls through their self‐generated vortices. This makes the latter example a topic for Complex Systems Research.