Euro notes and coins enter circulation in 12 European Union countries, in the biggest monetary changeover in history.

BBC News Online brings you coverage of the launch, the consequent impact, and looks at some of the issues surrounding the new currency.

The real test lies with Europe's public

'Crunch time'

The 12 participating countries were proud that the new currency's launch went smoothly on New Year's Day. But the real test lies with the citizens of those countries, who started using the euro in earnest on the following day - how easy would they find the transition?

 The BBC's Economics Editor Evan Davies

 BBC correspondents report on the everyday impact of the euro in some of the 12 eurozones

 The BBC's Paul Anderson reports from Kosovo and Montenegro where the euro is also being adopted as an official currency

The euro's effect will be felt well beyond its borders

'Dawn of a new era'

The euro becomes a reality for 300 million citizens in 12 European countries. As New Year dawns, many revellers head straight to cash dispensers to get their hands on the new notes.

 The BBC's Justin Webb reports from Brussels

 The BBC's Philippa Thomas presents a BBC News special on Europe coming to terms with its single currency

 The BBC's Evan Davis on how the euro is going down in Holland and Germany

 The BBC's John Pienaar: "The (UK) government hopes familiarity will win over the sceptics"

The euro is born

People partied on the streets of Paris as the euro was launched

As clocks strike midnight across Europe, ten years of planning comes to fruition. From the Greek Islands to the Arctic Circle, the new coinage is ushered in with public parties, fireworks and extravagant displays.

 BBC News special as the new currency is launched across Europe.

  European Central Bank President Wim Duisenberg: "A clear signal of the confidence and hope we have in tomorrow's Europe"

Leaders hail currency's success

Ireland's PM Bertie Ahern spent his first euros at his local newsagent

Despite a few teething troubles as businesses and the European public try to adapt to the euro, leaders across the EU declare themselves happy with the launch of the currency. The biggest cash switchover in history seems to have gone relatively smoothly, with little evidence of either counterfeiting or price rises.

 EU Commission President Romano Prodi: "Today is a great day for Europe"

 Irish Prime Minister Bertie Ahern in Dublin: "It's already been a tremendous success"

Long road to euro

The European Central Bank, one of the key creations in the run up to introducing the euro

Achieving monetary union has been a long and difficult process, with the question of whether to join dividing many nations across the continent. It has been a political act as much as an economic one, with attempts to create a single currency going back more than 20 years.

 The BBC's William Horsley examines how the euro came about

UK still split over the new currency

Peter Hain warns Britain risks losing influence in Europe if it does not join the single currency.

Britain, Sweden and Denmark have all opted not to join the euro with the rest of Europe. In the UK, pro-euro campaigners hope that the currency's launch will provide a boost to their argument that Britain should join in. But many euro sceptics say that however well or badly the currency performs, the country should stay out on a point of principle.

 The BBC's Helen Simms reports

 UK Minister for Europe Peter Hain:"'Britain should be at centre of Europe"

The central bank has distributed $600bn of notes and coins to member states

In August 2001 the European Central Bank put the new money on show. The multicolour notes come in denominations from five to 500 euros. The images of bridges, windows and gateways are designed to symbolise the new links between European countries.

 The BBC's Jonathan Charles reports from Frankfurt