This introductory chapter provides an overview of the book, and some words are devoted to the activity of interest: political protest. Institutional and non-institutionalized political activity will be distinguished. We will argue that people embark on institutional political activities in party politics and on non-institutionalized activities in movement politics. Non-institutionalized movement activities are defined as political protest. The central question underlying this volume is: why do some people protest, while others don’t? We aim to merge theory and evidence on protest politics whereby individuals always figure center stage – what are their fears, hopes, and concerns? What groups do they identify with? Are they cynical about politics or do they trust their authorities? What are the choices they make, the motives they have, and the emotions they experience? Why do they decide to stay or, for that matter, radicalize or leave the movement? The book takes a social psychological approach to contention. In doing so, this book provides three unique lenses to social movement literature, namely (1) The individual as a unit of analysis, (2) Contextualization of contestation, and (3) The individual aftermath of contention.