We decompose stock idiosyncratic volatility into long-run and short-run components and find that both are negatively related to delta-hedged option returns. The effect of the long-run component is explained by limits-of-arbitrage, while that of the short-run component is driven by stock jumps, which can be traced to corporate news releases. Unlike the long-run component, the short-run component can be used to create a trading strategy that remains profitable after considering transaction costs. In downturns, only the short-run idiosyncratic volatility effect is significant. Moreover, stock jumps also explain the relation between short-run idiosyncratic volatility and stock returns documented in prior literature.