The network paradigm dominated immunological research from the early 1970s to the late 1980s. The originator was Niels Jerne, who shared the 1984 Nobel Prize in Physiology or Medicine with G. Köhler and C. Milstein for his brilliant theories in immunology. Jerne hypothesized that the vast diversity of antibodies present in each individual form a network by mutual "idiotypic" recognition, thus regulating the immune system. By making the connection from this postulated "Eigenbehavior" to emerging concepts in systems biology including cybernetics, the network theory opened a whole new way of looking at the immune system, thus elevating immunology onto a higher intellectual level. Eventually, with the advent of exact scientific technologies, the network paradigm became subject to criticism and is now largely abandoned.This book is a first hand historical account of the rise and fall of the network paradigm, describing the main laboratories in the field with their scientific contributions, ways of experimenting and thinking. The description of the scientific aspects is complemented by personal interviews with most of the prominent protagonists and antagonists, disclosing their retrospective views on the network paradigm.