Collateralised debt obligations - toxic financial instruments at the heart of the credit crunch.
Banks embraced them as a way of shifting debt off their balance sheets, enabling them to lend more.
The first CDO is said to have been issued in 1987 by bankers at the now defunct Drexel Burnham Lambert. In 20 years, the size of the market is estimated to have reached $2 trillion, and boomed between 2004 and 2007.