This book describes the essentials of a mathematical description of thedynamics of biochemical networks. It covers both deterministic and stochasticaspects of the dynamics. After providing a brief introduction to basic molecularbiology, the book describes fundamentals of chemical kinetics. The chapter onsignal transduction makes contact with ideas from feedback circuit analysis andsignal processing. The chapter on switches and oscillators analyses in detailbiological examples, both natural and synthetic. Excitable systems areintroduced and contrasted with oscillators. The last chapter deals with patternformation and development and brings us to current questions of robustness ofperformance of developmental networks. The book provides brief introductions tosome of the mathematical tools required in the main text and in a dedicatedappendix. The emphasis, throughout, is on understanding of the essentialdynamical aspects rather than just on recipes to build complex models.