Here's how the Wall Street Money Machine worked in the run-up to the financial collapse: Banks created CDOs from mortgage-backed securities. Banks often retained the large top portion, called the "Super Senior." The bottom portion, or "Equity," was often sold off to hedge funds. The middle portion, or "Mezzanine," often went into new CDOs. The main buyers of those new CDOs were once again the banks.

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Related graphic: A Bank’s Best Customer: Its Own CDOs