A reworking of Grant Wood's famous painting of a 'homely, dependable-looking' mid-Western couple
By Greg Wood
BBC North America business correspondent
Fannie Mae and Freddie Mac sound like a homely mid-Western couple - dependable, perhaps slightly dull.
But these two almost destroyed the US housing market and their downfall was the overture to the global financial crisis.
On 7 September 2008, these giants of the financial world had to be nationalised by the US government.
Fannie Mae was a child of the Great Depression.
The Federal National Mortgage Association was set up in 1938. A government agency, its job was to buy home loans from mortgage providers.
The mortgage providers would use the money they received from Fannie Mae to make more home loans. Freddie Mac, set up in the late 60s, did the same thing.
But once Fannie and Freddie held all these mortgages on their books they had to do something with them.
Slice and dice
The answer was "securitisation". It's a process which works a bit like a layer cake.
2008 CRISIS TIMETABLE
7 SEPT: Fannie Mae nationalised
15 SEPT: Lehman bankruptcy
18 SEPT: Lloyds takes over HBOS
19 SEPT: $700bn US bail-out plan
29 SEPT: Bradford and Bingley nationalised
5 OCT: Bail-out plan agreed by Congress
12 OCT: UK bails out RBS and Lloyds-HBOS
You stack up all the mortgages horizontally and then slice them vertically.
Each slice contains a little bit of all the mortgages in the "cake" and can be sold on the financial markets as a "security" - an investment like a share or a bond.
But there was a flaw in the model.
If a sufficiently large number of homeowners defaulted on the underlying loans, then the value of those mortgage-backed securities would collapse.
Fannie Mae and Freddie Mac would also be landed with the - very large - bill for the mortgage repayments.
That's what began to happen when the US housing bubble burst in 2007.
Millions of people defaulted on their home loans. The value of mortgage-backed securities began to fall.
So too did the share prices of Fannie Mae and Freddie Mac.
Both organisations were incurring massive losses - $14 billion in the 12-month period up to September 2008 - as they paid out the guarantees on millions of bad home loans.
It was the first in a series of crisis Sundays as the US government grappled with a cascade of financial disasters
This put them desperately in need of new capital to fill the hole in their balance sheets.
But Fannie and Freddie had lost so much in the housing market that private investors were unwilling to provide the new money they needed.
They were on the brink of bankruptcy.
That event had the potential to trigger a collapse in the global financial system.
Fannie and Freddie, by this time privately owned, were the two biggest financial institutions on the planet.
Hank Paulson said Fannie and Freddie posed a risk to the entire system
Their bonds and securities were held by investors around the world, including many governments.
Together they owned or guaranteed half the mortgages in the United States - a staggering $5 trillion in home loans.
Fannie and Freddie were then responsible for financing 80% of all new mortgages in the US.
If they went bust it would be almost impossible for anybody in the States to get a home loan.
This was the situation facing the government as it entered the weekend of 6 and 7 September a year ago.
By the Sunday, the fateful decision had been made and Hank Paulson strode down the steps of the Treasury Department building in Washington DC like some prophet of doom with his gaunt expression and whispering voice.
The condition of Fannie Mae and Freddie Mac posed a "systemic risk" to the entire financial edifice, he told the nation.
They could not continue in the present state, so the government was taking them into "conservatorship".
In plain language, these twin pillars of the mortgage market were being nationalised.
It was the first in a series of crisis Sundays, as the US government grappled with a cascade of financial disasters in the hope of resolving them before the markets re-opened for business at the start of another fraught week.
The nationalisation of Fannie Mae and Freddie Mac was supposed to draw a line under the financial crisis.
Instead, it merely acted as a prelude to the far more shocking events that were soon to unfold before an astonished world.