How was the Banking Union, the most advanced legal and institutional integration in the single market, created? How does European law impact European integration? To answer these questions, this book provides a sweeping account of the evolution of European law. It identifies five integration periods of the single financial market, intertwined with the development of global finance, from its origins, through its expansion and crisis, to the Banking Union. Each period is defined by innovations to deepen integration, such as the single passport for financial services, soft governance and comitology, agencies, or a single rulebook. Providing a far-reaching explanation of the legal and institutional rationality of the European Banking Union, this book demonstrates that the Banking Union is not an accident of history or simply the product of the existential crisis of the Monetary Union. It has deep roots in the evolutionary process of European law and its drive towards supranational integration.