Diatoms are any member of a large group comprising several genera of microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of the Earth's biomass. They generate about 20 to 50 percent of the oxygen produced on the planet each year!
Diatoms are unicellular organisms: they occur either as solitary cells or in colonies, which can take the shape of ribbons, fans, zigzags, or stars. Individual cells range in size from 2 to 200 micrometers.
The unique feature of diatoms are that they are surrounded by a cell wall made of silica (hydrated silicon dioxide), called a frustule. These frustules produce structural coloration, prompting them to be described as "jewels of the sea"