Media research in the 21st century must first overcome the media fundamentalism that assumes, a priori, that media both convey and create what they communicate. In the digital age, the medium is not only the message but also the platform for communicative actions of self-presenting subjects. Media influences individuals, and at the same time, individuals—more than ever, more actively than before—interact with media. This book illustrates and analyzes the historical, cultural sociological, and media development lines from classic youth cultures to the social networks of today. Based on a research project from the Institute for Cultural and Media Management at the Free University of Berlin, it addresses the profound changes in the understanding of "youth" and "youthfulness.".