The book presents a collection of mathematical tools, modeling approaches and numerical recipes used in age structured modeling, showcased via a substantial number of concrete examples, all worked out and discussed in great detail. More importantly, it retains the same clarity and attention to detail, which makes the book suitable for a graduate course in age structured epidemiological modeling, the reader being constantly guided via comments, motivations and proof details that are not usually spelled out in articles. (Paul Georgescu, Mathematical Reviews, March, 2022)