The word "diatomaceous" comes from the root word "diatom", which is a single-celled organism found in freshwater lakes and riverbeds. Diatomaceous earth is a chalk-like powder that is made up entirely of these diatoms that have fossilized over thousands of years. Depending on the grade of diatomaceous earth, these diatoms can be used to promote health, preserve food, and even control many common household pests & insects.