This is considered the first major test of the eurozone since its 1999 launch
PIGS is a horrible acronym.
But this is how the financial markets refer to the troubled and heavily-indebted countries of Europe - Portugal, Ireland, Greece and Spain.
(Some analysts use PIIGS to include Italy - Europe's longstanding biggest debtor.)
Greece has dominated the concerns of investors since late last year, when concerns over whether it will be able to pay off the 300bn euros ($419bn; £259bn) in government debt it currently owes.
The euro has been battered over the past month as some even started to fear the break-up of the eurozone.
Now the European Union has agreed a deal to rescue Greece - with perhaps other wrecked economies to be helped at a later date.
Just how bad a situation are the PIGS in, and how does that compare with the UK?
Economy, in European Union: 11th largest
Latest GDP figure: -0.3% (Third quarter of 2009)
Gross debt in 2010, forecast: 125% of GDP
Gross debt in 2007: 94.5% of GDP
Jobless rate: 9.7%
Stocks performance in 2010: -10.5% (to 11 February)
Greece benefited from joining the euro in 2001. But the Greek government went on something of a spending spree and public spending soared.
Now, it is suffering from its huge spending - and widespread tax evasion - as it finds itself unable to cope with its huge debt loads and meet EU deficit rules. Greece's deficit is, at 12.7%, more than four times higher than European rules allow.
It remains to be seen whether the EU's deal on Greece will help soothe markets, and ease concerns over other indebted nations.
Economy, in European Union: 13th largest
Latest GDP figure: 0.3% (Third quarter of 2009)
Gross debt in 2010, forecast: 82.9% of GDP
Gross debt in 2007: 25.4% of GDP
Jobless rate: 13.3%
Stocks performance in 2010: -1.5% (to 11 February)
The Irish Republic was one of the biggest success stories of the recent boom, with its economy nicknamed the "Celtic Tiger". But its economic growth was dependent on a property bubble.
It became the first eurozone country to fall into recession in 2008. It has pumped 7bn euros into its two biggest banks, Allied Irish Banks and Bank of Ireland, and created a state-run agency to handle their bad debt.
The Irish economy emerged from recession last year, but there was widespread public anger at the level of public spending cuts that have been made.
Economy, in European Union: Fifth-largest
Latest GDP figure: -0.1% (Fourth quarter of 2009)
Gross debt in 2010, forecast: 66.3% of GDP
Gross debt in 2007: 36.2% of GDP
Jobless rate: 19.5%
Stocks performance in 2010: -13% (to 11 February)
Spain has been very hard-hit by huge declines in its property markets. With recent figures showing its economy contracted in the last three months of 2009, Spain remains the last major economy in Europe still in recession.
While its banks have withstood the economic downturn better than in the Irish Republic or the UK, the government announced a 50bn-euro austerity package, including a civil service hiring freeze, at the end of January.
With the International Monetary Fund expecting Spain to contract by 0.6% in 2010 - compared with predicted growth for the 16-nation eurozone - many investors feel it will be the next country to rattle financial markets.
Economy, in European Union: 15th largest
Latest GDP figure: 0.9% (Third quarter of 2009)
Gross debt in 2010, forecast: 84.6% of GDP
Gross debt in 2007: 63.6% of GDP
Jobless rate: 10.4%
Stocks performance in 2010: -9.7% (to 11 February)
Portugal - with its high borrowing and sudden reversal in economic fortunes - has been lumped in the same category as its Mediterranean neighbours.
The country has vowed not to leave the eurozone, with its finance minister telling the BBC that it faced "an extraordinary and exceptional situation, due to a major financial and economic crisis without precedent in our recent history".
Economy, in European Union: Third-largest
Latest GDP figure: 0.1% (Fourth quarter of 2009)
Gross debt in 2010, forecast: 80.3% of GDP
Gross debt in 2007: 43.8% of GDP
Jobless rate: 7.8%
Stocks performance in 2010: -4.2% (to 11 February)
Although the UK did officially come out of recession in the fourth quarter of 2009 - ending six consecutive quarters of economic decline - the growth was just 0.1%, much less than expected.
The UK government spent £85.5bn last year on bailing out the banks. Now, Chancellor Alistair Darling is predicting a record £178bn of borrowing in the current fiscal year.
With an election this year, Labour and the Conservatives have been sparring over the exact size of spending cuts and many economists have raised concerns that the UK could have its credit rating cut.