Diatomaceous earth is a naturally occurring substance made up of the fossilized remains of tiny aquatic organisms called diatoms. The sharp edges of these fossils can cut through the exoskeletons of insects, causing them to dehydrate and die. This same effect can also be used to get rid of mice. To use diatomaceous earth to get rid of mice, simply sprinkle it around areas where you've seen them or where they are likely to travel. Be sure to apply it liberally, as mice can easily avoid small patches. You'll need to reapply diatomaceous earth every few days, but it's otherwise a safe and effective way to get rid of these pests.