Diatomaceous Earth is a naturally occurring, soft sedimentary rock that consists of skeletal fragments of diatoms. Diatoms are single-celled algae with hard shells made of silica. These tiny creatures live in oceans and freshwater bodies around the world, and their remains accumulate over time to form deposits of diatomaceous earth. This material has a number of uses including as a filter agent, abrasive, and for killing pests like ants, cockroaches, and fleas by dehydrating them when they come into contact with it.