The European Council and the Council of the EU are two key players in the EU's decision-making process. Each has its own distinct role in the EU's institutional architecture, even though politically and administratively a close organic relationship exists between both institutions. Both bring together representatives of the member states. This booklet traces their origins and evolution through the EU treaties. It explores how they both played a decisive role in European integration and how their history reflects that of the EU as a whole: its policies and ambitions, its crises and progress.