The Euro

The Euro is the official form of currency used by 17 countries within the European Union, or EU.  Since it's initial launch in 1999 it has replaced the former currencies of it's members, such as the German Deutschmark and the French franc.  Back then, only 11 countries were a part of the two-part transition from their original currencies and the Euro.  First, the Euro was used for accounting purposes while most people still used their national currencies for cash payments.  However, by 2002 the Euro circulated in the form of coins and banknotes.  Although a number of countries have decided to use the Euro, a few have decided to stay with their regular forms of currency. Some of these included Great Britain, Denmark, and Switzerland.  In the last few years six more countries have signed on to using the Euro, only to find it's current state in crisis, with the Euro's value dropping.  In addition, several countries that use the Euro have faced economic crisis. Greece has fared the worst, with an eventual bailout from Germany.  Only time will tell whether the EU and the Euro itself will survive and accomplish it's original goal of unifying all of Europe's currency.

Sources:

http://ec.europa.eu/economy_finance/euro/

http://www.gocurrency.com/countries/euro