An attempt was made to include rather common systems in this selection, i.e. system structures that are encountered again and again in modeling real sys tems and describe important processes of our everyday experience ("everyday dynamics"). Mathematical curiosities that have no counterpart in the real world were not included. The collection is limited to systems with at most four state variables. Many of the "system animals" included in the systems zoo are found as subsystems in more complex systems. This has already been pointed out during the development of the three models in the first part of the book which contain important elementary structures (exponential growth or decay, logistic growth, delay, oscillation, predator-prey relationship). The acquaintance with these ele mentary systems can help in understanding much more complex systems.