This is the Fed's balance sheet. This is the Fed's balance sheet on junk securities. It's hard to read, but the gist is that the gray area represents Treasury securities -- debt owed by the U.S. government, which has been the Fed's traditional asset. The non-gray stuff, which as you can see began to teem and fester in December, is risky, private-sector debt that the Fed took on in return for swapped Treasury securities to financial companies that needed propping up. Note the vertical scale -- we're measuring in terms of hundreds of billions of dollars. Sometimes it's easy for forget how extraordinary the last six months has been. This is a reminder. The chart is via Calculated Risk.