Over the past few years, the Fed bought $1.25 trillion* of mortgage bonds.

It was a big move for the central bank, intended to prop up the housing market. But in all the discussion about the program, we never heard anybody explain how you actually buy all those bonds.

On today's Planet Money, we go inside the Fed to find out.

  http://www.npr.org/blogs/money/2010/08/31/129558498/the-tuesday-podcast-how-to-spend-1-249-999-999-999-39