EU referendum: What is the EU?
On 23 June there will be a referendum in the UK on whether to remain in or leave the European Union.
But what is the EU?
After World War Two a plan was drawn up to try and ensure peace through economic cooperation in Europe.
In 1950, six countries signed a deal to create a common market for their coal and steel resources.
Seven years later a treaty signed in Rome created the European Economic Community - an agreement to create a free trade area.
In 1973 the UK joined, along with Ireland and Denmark.
And today 28 countries are members of what is now called the European Union.
Free movement of goods, services and people between countries is still a key objective.
But now the EU also has interests in reducing regional inequalities, protecting the environment, security, education and human rights.
Many members - but not the UK - share the same currency, the euro.
Some people feel the EU has taken too much power away from individual nations, but others argue for closer integration.