Written for students and researchers in systems biology, the second edition of this best-selling textbook continues to offer a clear presentation of design principles that govern the structure and behavior of biological networks, highlighting simple, recurring circuit elements that make up the regulation of cells and tissues. Rigorously classroom-tested, it contains new additions as well as corrections and revisions for better flow. This edition includes seven new chapters on exciting advances made in the last decade, and over double the number of exercises.