The euro is the result of the European Union's project for
economic and monetary union that
came fully into being on 1 January 2002 and it is now the currency used by the majority of the
European Union's member states, with all but Denmark (which has an
opt-out in the EU treaties) bound to adopt it. It is the currency used by the
institutions of the European Union and in the failed treaty on a
European Constitution it was to be included with the
symbols of Europe as the formal currency of the European Union. The euro is also
widely used by other states outside the EU. Except for Denmark, all current and future members of the EU are obliged to adopt the Euro as their currency, thus replacing their current ones. The relationship between euro and non-euro states has been on debate both during the United Kingdom's membership (as a large opt-out state) and in light of
withdrawal from the EU and how that impacts the balance of power between the countries inside and those outside the eurozone, avoiding a eurozone caucus out-voting non-euro states. Former member United Kingdom had called for the EU treaties to recognise the EU as a "multicurrency union", which sparked concerns about undermining euro adoption in remaining countries. ==Current currencies==