After 47 years of membership, the United Kingdom left the European Union - the single market and customs union - in 2020.

Croatia becomes the 28th member of the European Union in 2013.

The Lisbon Treaty enters into force in 2009. The most important changes brought by the Treaty are two new functions within the institutional system of the European Union: the President of the European Council and the High Representative of the Union in the field of foreign policy and security policy in order to strengthen the position of the European Union on the international stage.

Romania and Bulgaria became members of the European Union in 2007.

Estonia, Cyprus, Latvia, Lithuania, Malta, Hungary, Poland, Slovakia, Slovenia and the Czech Republic become members of the European Union.

The Nice Treaty of 2003 prepares a major enlargement with 10 new member states. The idea of the Constitution of the European Union is emerging.

The euro became the official currency of the European Union in 2002.

The Treaty of Amsterdam from 1999 introduces an obligation to the communities to increase the employment rate, as well as to create unity between the member countries in the area of protection of basic human rights, every kind of freedom and security of European citizens.

Austria, Finland and Sweden joined the European Union in 1995. At the same time, the Schengen Agreement, which abolishes the borders between the signatory countries, enters into force, and the EU gains powers in the field of immigration, control of the external borders of the Schengen zone and approval of visas and asylum for citizens of other countries.

By the Treaty of Maastricht in 1993, all three communities were merged into one called the European Union. The basic idea of the new community is the creation of a common foreign, monetary and security policy. Then the three pillars of the EU are created:

• I pillar: Community;
• II pillar: Common foreign and security policy;
• III pillar: Joint judicial and police cooperation in criminal matters.

Spain and Portugal became members of the European Union in 1986, when the Single European Act was adopted, giving the parliament greater powers (it entered into force in 1987).

Greece joined the community in 1981.

The first expansion took place in 1973, when Denmark, Ireland and Great Britain joined the Community. Norway was supposed to join the Community in this enlargement, but the referendum voted against joining.

The agreement entered into force in 1967 (it was signed in 1965) and all three communities received common bodies: the Commission, the Council of Ministers and the Parliament. The headquarters of the institutions are in Brussels, Luxembourg and Strasbourg.

It soon became clear that the Coal and Steel Community was not enough, so in 1958 the European Economic Community and the European Atomic Energy Community (EURATOM) were founded. The idea was to create a common market that allows free movement of goods, people, capital and services, abolish trade restrictions, harmonize economic and social policies, as well as standardize customs duties, and help underdeveloped regions of member states.

The European Coal and Steel Community, as the first form of unification, was created in 1952. The contract was concluded for 50 years and expired in 2002. The founding countries of the first Community are: France, Germany, Italy, Belgium, Luxembourg and the Netherlands.