The fifth edition has been fundamentally revised, updated, and expanded. It focuses on presenting important milestones and ways of thinking in media effects research; the core statements are summarized and explained with examples. Methodological and theoretical aspects are given attention, as well as the historical background or context of the respective questions. Following the introductory remarks on the development of mass media, there are extensive presentations of significant research traditions and hypotheses that address the question of what communication can achieve. The conclusion is a chapter with observations on the future of media.