EU is a stage in the process of European integration. Realized in dynamical sense EU was established under influence of ideas of European movements, in conditions of a hard economical situation and intricate political relationships. The first European community was established in Paris on 18th April 1951. It was European Coal and Steel Community (ECSC). The other European communities were established in Rome on 25th march 1957. Those are European Economic Community and EUROATOM. EU was established by Treaty on European Union that was signed in Mastricht, a small Netherlands's town, on 7th February 1992. It was done a reform of European communities by Treaty on EU as well. There had already been reforms of EC. The most important was this one done by Single European Act (1986). Last reform of EC that described in the article was done by Treaty of Amsterdam (1997). Institutions of EU are: European parliament, Council, Commission, Court of Justice and Financial court. Council is not the same as European Council, a political body regulated by Treaty of EU. First instance court was added to Court of Justice on 1989. Consultative bodies of EU are: Economic - social Committee and Regional Committee. An important financial institution of EU is European investment bank. Organ for administrative control is Ombudsman. Sources of EU law are divided on primary and secondary ones. Primary sources of communitarian law are: establishing contracts, international agreements among EU-member-states and international agreements between Community and non-member-states or international organizations. Secondary legislature of EU are: regulations, directives, decisions, recommendations and opinions. There may exist sui generis legal acts. Particularly mentioned: general legal principles and precedents. At the end author concludes that EU law has a supremacy above national law of member states.