The world consists of many complex systems, ranging from our own bodies to ecosystems to economic systems. Despite their diversity, complex sys tems have many structural and functional features in common that can be effectively modeled using powerful, user-friendly software. As a result, vir tually anyone can explore the nature of complex systems and their dynam ical behavior under a range of assumptions and conditions. This ability to model dynamic systems is already having a powerful influence on teaching and studying complexity. The books in this series will promote this revolution in "systems think ing" by integrating skills of numeracy and techniques of dynamic modeling into a variety of disciplines. The unifying theme across the series will be the power and simplicity of the model-building process, and all books are de signed to engage readers in developing their own models for exploration of the dynamics of systems that are of interest to them. Modeling Dynamic Systems doesnot endorse any particular modeling paradigm or software. Rather, the volumes in the series will emphasize sim plicity of learning, expressive power, and the speed of execution as priori ties that will facilitate deeper system understanding.