Whereas price extremes have no boundaries, they don't last forever, eventually commodity market supply and demand factors will bring prices back to a more equilibrium state. Accordingly, while caution is warranted at extreme levels it is often a good time to be constructing counter trend trades as it could be one of the most advantageous times in history to be involved in a market. For instance, similar to the idea of call options being over-priced when a market is at an extreme high, the puts might be abnormally cheap. Once again, your personal situation would determine whether an unlimited risk or limited risk option strategy should be utilized. Please realize that identifying extreme pricing scenarios is easy, it is much more difficult to predict the timing necessary to convert it into a profitable venture.
An option is a contract that allows (but doesn't require) an investor to buy or sell an underlying instrument like a security, ETF or even index at a predetermined price over a certain period of time. Buying and selling options is done on the options market, which trades contracts based on securities. Buying an option that allows you to buy shares at a later time is called a "call option," whereas buying an option that allows you to sell shares at a later time is called a "put option."