Presently there is an information overflow in immunology (one article appears every 20 minutes). The book, by describing, analyzing and conceptualizing several seminal discoveries is particularly useful for young scientists but also for the more mature, who use "puzzling or not puzzling" as a major but commonly misleading selection criterion. The book summarizes the major events in the construction of the immunology-tower during a period roughly corresponding to the last third of the 20th century, the era when most questions about the biology of the immune system were raised and also found their answers. Written by an "eyewitness," it provides a concise introduction to the following topics: immunological specificity,