First introduced in 1999 as book money, the euro has become one of the most important currencies in the world.
The coins and banknotes were rolled out in 2002 in 12 EU countries: Austria, Belgium, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, the Netherlands, Portugal, and Spain.
Now, the euro area includes 19 European Union member states. The overseas territories of some of these countries also use the currency.
Croatia will soon join the eurozone as its 20th member at the start of next year. European finance ministers officially approved the measure last month.
But these aren't the only states that use the euro. Watch our video report to find out which countries use also use the currency in the player above.