Volume I examines the history of the European Union from an outside-in perspective, asking the following questions: how does the European Union look from the outside, and which outside forces shaped and guided the process of European integration? Split into three parts, the first addresses the main external events that have steered the European integration process, with emphasis placed on critical junctures following the Second World War, such as the division and reunification of Germany and the Eastern enlargement. Part II considers the various international trends that have shaped European integration, with particular focus on globalisation and geopolitics. While the first two parts pay special attention to institutions, countries, international organisations and the main actors, Part III focuses on the role of ideas, networks, public opinion and memory that influenced the development of the European Union.

Volume II examines the history of the European Union from an inside-out perspective, focusing on the internal developments that shaped the European integration process. Split into three parts, Part I covers the principles that have defined European integration, exploring the treaties and their changes through time, with Brexit being a core milestone. Part II considers the different instruments within the architecture of European integration, with special focus on the development of policies, the euro and enlargement. Part III concentrates on the various narratives surrounding European integration, in particular the concepts, goals and ideas that both spoke and failed to speak to the hearts and minds of Europeans. This includes the 'longue durée' concept, peace, European culture, (the absence of) religion, prosperity and (a lack of) solidarity and democracy.