The Maastricht Treaty, officially known as the Treaty on European Union, laid the foundations for a single European currency and for the European Union as we know it today. The Treaty was signed by 12 countries in Maastricht on 7 February 1992 and came into force on 1 November 1993. It was the culmination of several decades of debate on closer economic cooperation in Europe. It lays down a three-stage process for the establishment of the Economic and Monetary Union. The third stage, which comprises the introduction of the single currency, began on 1 January 1999. In addition, the Treaty sets out the rules or convergence criteria to be met by countries wishing to join the euro area.