This paper provides an up-to-date overview of the gradual development of differentiated integration and the ensuing changes in the nature of European integration. It considers the dynamics of deepening and widening of the EU and proposes the metaphor of a ‘European Onion’ that is designed to capture the bigger picture. Further, this paper expands upon the centripetal effects of differentiated integration and shows its potential to generate more cooperative public opinion in future enlargement rounds. Finally a state of play in European integration theory is offered that incorporates differentiated integration. © 2007, Taylor & Francis Group, LLC.
