This introduction presents an overview of key concepts discussed in the subsequent chapters of this book. The book explores dimensions of inequality, domination, exclusion, and their rationalization through the freedom of movement and the control of frontiers in the European Union, in a theoretically explicit, comparative, and empirically grounded fashion. It examines the process at work at the level of the European Union and the differences that it is creating, in comparison with the US. The book discusses Foucault and Bauman concerning the nature of the frontier controls in the European Union, and offers a comprehensive vision that permits the reader to understand better the notions of frontiers, security, and identity in the European context. It looks at the heterogeneity of concrete situations and analyzes the diagram of forces which gives them their originality and at the same moment allows comparisons. The book emphasizes some of the main features of domination and inequalities.