60 Minutes' Steve Kroft examines the complicated financial instruments known as credit default swaps, and reveals how these little-known derivatives played a central role in precipitating the current market meltdown. In essence, speculators bet that homeowners wouldn't be unable to pay back their mortgages, and when those people started defaulting and the speculators tried to cash in their wagers, there was no money to cover the literally trillions of dollars in payouts. What it really boils down to is an unregulated gambling racket that Congress voted unanimously to create and legalize.

The world's financial system teetered on the edge again last week, and anyone with more than a passing interest in their shrinking 401(k) knows it's because of a global credit crisis. It began with the collapse of the U.S. housing market and has been magnified worldwide by what Warren Buffet once called "financial weapons of mass destruction."

They are called credit derivatives or credit default swaps, and 60 Minutes did a story on the multi-trillion dollar market three weeks ago. But there's a lot more to tell.

As Steve Kroft reports, essentially they are side bets on the performance of the U.S. mortgage markets and the solvency on some of the biggest financial institutions in the world. It's a form of legalized gambling that allows you to wager on financial outcomes without ever having to actually buy the stocks and bonds and mortgages.

It would have been illegal during most of the 20th century, but eight years ago Congress gave Wall Street an exemption and it has turned out to be a very bad idea.