Estonia has become the 17th member of the eurozone – the first ex-Soviet state to adopt the EU single currency.
The changeover from the kroon to the euro started at midnight (2200 GMT) in the small Baltic nation of 1.3m people.
Despite market pressure on the eurozone and the Greek and Irish bail-outs this year, polls suggested most Estonians wanted the euro.
Prime Minister Andrus Ansip marked the event by withdrawing euros from a cashpoint.
“It is a small step for the eurozone and a big step for Estonia,” he said, holding the euro notes.
For many Estonians, 20 years after breaking away from the Soviet Union, the euro is proof that they have fully arrived in the West, the BBC’s Baltic region correspondent, Damien McGuinness, reports.
Estonia joined the EU in 2004 – one of eight former Communist countries that did so, including its Baltic neighbours Latvia and Lithuania.
Two other ex-Communist countries – Slovenia and Slovakia – are already in the eurozone.
BBC News