Now that the UK has voted to leave the EU, it's a major blow to the European Union system. The UK is not the only country that has had a problem with the European Union.

Denmark and Sweden are EU member countries but like the UK, they refused to adopt the Euro. Switzerland is not part of the European Union and has kepit its access to the Union's single market.

The European Union has seen increasing political and economic integration among member states since its official establishment in 1993, after the The Maastricht Treaty came into force.

But tough problems remained unresolved. The long-standing debt problems for one, have evolved into a debt crisis that weighed on the whole continent for the past few years.
And there are immigration issues. The recent migrant crisis saw this tension intensify, and partly leading to the UK referendum.