Originally based on a graduate course taught by the author, this true classic has once again been extensively updated to incorporate key new findings in biological signaling. With over half of the content re-written, plus 70 brand new and 50 revised figures, this is the most up-to-date textbook on signaling available anywhere. Thanks to its clear structure, hundreds of illustrative drawings, as well as chapter introductions and newly added study questions, this text excels as a companion for a course on biological signaling, and equally as an introductory reference to the field for students and researchers. Generations of students and junior researchers have relied on "the Krauss" to find their way through the bewildering complexity of biological signaling pathways.