The purpose of this paper is to use insights from the academic literature on crises to understand the role of liquidity in the current crisis. We focus on four of the crucial features of the crisis that we argue are related to liquidity provision. The first is the fall of the prices of AAA-rated tranches of securitized products below fundamental values. The second is the effect of the crisis on the interbank markets for term funding and on collateralized money markets. The third is fear of contagion should a major institution fail. Finally, we consider the effects on the real economy.