Here is a look back at the main milestones for the European Union after it was awarded the Nobel Prize for Peace on Friday:
1950 - French Foreign Minister Robert Schuman launches plan to put West German and French coal and steel industries under single authority, aiming to make war between the two countries "materially impossible".
April 1951 - France, West Germany, Italy, Belgium, Luxembourg and the Netherlands sign Treaty of Paris creating European Coal and Steel Community (ECSC).
March 25, 1957 - Six founding nations - France, Germany, Italy, the Netherlands, Belgium and Luxembourg - sign the Treaty of Rome establishing European Economic Community (EEC), a common market with free movement of goods, capital, labour and services.
July 1, 1967 - European Community (EC) is formed by merging the EEC with the European Atomic Energy Community (Euratom) and the European Coal and Steel Community (ECSC), both created by the same six founder nations.
1974 - The European Council is created as an informal forum for discussion between heads of state and government, and became one of the seven EU institutions in December 2009.
March 1979 - Exchange Rate Mechanism (ERM) is formed, linking German mark, French and Belgian francs, Dutch guilder, Danish crown, Irish punt and Italian lira within narrow bands.
December 1991 - Maastricht Treaty on Economic and Monetary Union sets timetable and conditions for a single European currency by 1999, a common foreign and security policy, and cooperation on justice and home affairs. The EC is renamed the European Union.
January 1999 - Euro is launched as a paper trading currency with 11 participating members. Euro notes and coins go into circulation in 12 countries in January 2002, replacing national currencies.
December 2007 - The now 27 EU countries sign the Treaty of Lisbon, superceding Maastricht. Critics argue that the new treaty strengthens the centralised powers of the bloc and, by moving powers away from national governments, erodes democracy. It is ratified on December 1, 2009.
December 2009 - Greece raised its deficit estimate to twice its original size, triggering a still-raging economic crisis in the euro zone and leading all EU member states - except Britain and the Czech Republic - to sign a March 2012 treaty designed to enforce more budget discipline.
Sources: Reuters/European Union websites
(Reporting by David Cutler, London Editorial Reference Unit; Editing by Louise Ireland)