The world consists of many complex systems, ranging from our own bodies to ecosystems to economic systems. Despite their diversity, complex systems have many structural and functional features in common that can be effec­ tively simulated using powerful, user-friendly software. As a result, virtually anyone can explore the nature of complex systems and their dynamical be­ havior under a range of assumptions and conditions. This ability to model dy­ namic systems is already having a powerful influence on teaching and study­ ing complexity. The books is this series will promote this revolution in "systems thinking" 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 designed to engage the reader in developing their own models for exploration of the dy­ namics of systems that are of interest to them. Modeling Dynamic Systems does not endorse any particular modeling par­ adigm or software. Rather, the volumes in the series will emphasize simplic­ ity of learning, expressive power, and the speed of execution as priorities that will facilitate deeper system understanding.