Diatom

Diatoms are a large group of mostly single-celled algae, found throughout the oceans, waterways and soils of the world, that function as a major component of phytoplankton. Their defining feature is a cell wall made of silica called a frustule, prized for its intricate, glasslike structure. Diatoms are classified among the stramenopiles in the division Ochrophyta and are estimated to generate between 20 and 50 percent of the oxygen produced on Earth each year, while making up nearly half of the organic material in the oceans. Roughly 12,000 species have been formally described, though scientists believe many more remain undocumented.