On May 6, 2010, several U.S.-based equity products underwent an extraordinary price decline and recovery, all within less than half an hour. The Dow Jones Industrial Average (DJIA) and other equity indices dropped by more than 5 percent in a matter of minutes, only to rebound as quickly. Individual equity securities experienced similar, if not larger, swings in prices, both up and down. This post describes what happened on that fateful day, and summarizes the findings of the academic literature on this topic.