The euro is the [[EU]]'s single currency. It was introduced as the EU's unit of account in 1999 by the 11 euro zone countries that joined stage three of [[EMU|EMU]]. Euro notes and coins were introduced in 2002. Sixteen countries use the euro as of 2009. | The euro is the [[EU]]'s single currency. It was introduced as the EU's unit of account in 1999 by the 11 euro zone countries that joined stage three of [[EMU|EMU]]. Euro notes and coins were introduced in 2002. Sixteen countries use the euro as of 2009. |