The document discusses the evolution of monetary unions in Europe, beginning with the Snake arrangement in the 1970s which established narrow fixed exchange rate bands between EEC currencies. This was replaced by the European Monetary System (EMS) in 1979, which aimed to coordinate exchange rate policies and pave the way for a European Monetary Union. The EMS used the European Currency Unit (ECU) and Exchange Rate Mechanism (ERM) to manage exchange rates within fluctuation bands. The Maastricht Treaty of 1991 furthered monetary integration by setting criteria for countries to irrevocably fix exchange rates by 1999 and introduce a common currency, establishing the European Central Bank and launching the Eurozone.