This book gives a detailed analysis of the making of the Treaty of Nice, the current treaty of the European Union, adopted in 2000. It analysis the interests and strategies of the various actors, including the 15 Member States, during the negotiations and tries to explain the main institutional changes: re-weighting of votes in the Council of Ministers, future changes in the composition of the European Commission, extended use of qualified majority voting and easier conditions for a smaller group of Member States going faster in the integration process ('enhanced cooperation').