Dehydrating food is a good way to preserve it; raisins, which are dehydrated grapes, are a good example. Dehydration through industrial processes makes it possible to keep food even longer and store it in a smaller space. Freeze-drying produces food that only needs rehydration—that is, the addition of water—to restore its original consistency. Runners, cyclists, and hikers fearful of dehydration seem to be constantly hydrating themselves nowadays, sometimes even using a shoulder pack with a tube going straight into the mouth. Dehydrate can also be used for making something "dry" or "lifeless;" thus, a dull teacher can dehydrate American history, and an unimaginative staging can dehydrate a great Shakespeare play.