Estuarine mud, the rivers and oceans are teeming with diatoms, single celled algae. Diatoms are responsible for processing between 20/50% of planetary oxygen through photosynthesis. When they die they sink down lower to form a carbon trap before eventually fossilising (as diatomite) as part of the formation of oil lakes in the deep ocean floor.
They are made of transparent silica found in sand and glass and used in ceramic glazes.
Digital light microscopy with Chris Neal.