Abstract
This chapter provides an overview of the European Union and its member states. It first explains why the member states matter in the EU before discussing the role of member states in the EU, with particular emphasis on three approaches to understanding member state–EU relations: intergovernmentalism, institutionalism, and governance approaches. It then examines the Europeanization of the member states as well as the revival of domestic politics approaches, which claim that it is impossible to understand the EU in light of its politicization during the 2010s. It concludes by presenting the logic and structure of this volume: how the relationship between the EU and its member states will be portrayed in the chapters that follow.