The euro is one of the most ambitious economic projects of our time. But during the recent Greek financial crisis, there were fears about its ability to survive as the shared currency of most European Union countries.
The euro recovered strongly from the near collapse of the world's banking system last year.
Some may argue the exports of larger economies, particularly Germany's, have grown because of the euro's relatively low exchange rate.
But doubts about the Greek government's ability to repay its debts has caused the cost of borrowing for the other weaker euro zone countries - such as Portugal, Ireland, Italy and Spain - to rise.
And the countries with stronger economies, especially Germany, now have to find the cash to keep Greece afloat. This huge operation breaks a key rule agreed by the euro zone countries - one which banned bailouts for nations which lived beyond their means.
Over the past decade, the euro zone has expanded rapidly to include many developing economies in eastern Europe.
But given the stresses and strains resulting from the credit crunch, can economies of such widely different strengths continue to share a single currency?