European politics has been reshaped in recent decades by a dual process of centralization and decentralization. At the same time that authority in many policy areas has shifted to the supranational level of the European Union, so national governments have given subnational regions within countries more say over the lives of their citizens. At the forefront of scholars who characterize this dual process as 'multi-level governance,' Liesbet Hooghe and Gary Marks argue that its emergence in the second half of the twentieth century is a watershed in the political development of Europe. Hooghe and Marks explain why multi-level governance has taken place and how it shapes conflict in national and European political arenas.