After a long period of war, European officials saw political and economic union as the only certain guarantee of peace in the future.
In 1950 French foreign minister Robert Schumann suggested the creation of a unified coal and steel community. The European Coal and Steel Community (ECSC) came into existence in 1951.
The original six members of the community included Belgium, West Germany, Luxembourg, France, Italy and the Netherlands.
As it started evolving, ECSC was to soon include other economic activities besides coal and steel production. 1957 witnessed the creation of the European Atomic Energy Community (EURATOM) and the European Economic Community (EEC).
To further integration, these three organisations merged in 1967 to have a single Commission, Council of Ministers and European Parliament.
Co-operation became stronger in 1992 through the signing of the Treaty of Maastricht.
The treaty envisioned further ties between state governments in areas like justice and home affairs. Because of these strengthened ties the Maastricht Treaty is often seen as the moment marking the creation of the nowadays European Union.
From that point on union members started thinking of furthering ties and coming up with mechanisms for common decision making. Areas of co-operation increased over time.
One issue that required more effort was the establishment of a common market and the removal of trade barriers within the union.
Further economic co-operation was to come through the introduction of a single currency, the euro. It was introduced on January 1 2002, when 12 out of the 15 member states adopted the euro in place of national currencies.
Once the union was established, it moved on to the enlargement process and to accepting new members.
In 1973 Denmark, Ireland and UK joined the original member states. An enlargement in 1981 saw the accession of Greece, followed by Spain and Portugal in 1986 and by Austria, Finland and Sweden in 1995.
The latest and biggest enlargement wave featured the EU entry of 10 new member states in 2004. Among these were Central European countries. The new union members featured the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia, Slovenia and Cyprus.
After a long period of talks and an extensive reform process, Bulgaria and Romania received an EU entry go-ahead and are to join the union on January 1 2007.
Shortly before the EU entry of the two countries, union officials said that the enlargement process might need to slow down until institutions adjust to the bigger number of member states and until the process of approving the common European Constitution gains some speed.
Source: europa.eu