Diatoms are a common form of algae.

They can exist as single cells or as colonies of cells.

Diatoms can live in both fresh water and salt water. They also live in soil.

An enormous number of diatoms live in the Earth's oceans, where they play a very important role in producing organic molecules and oxygen through photosynthesis.

Diatoms Viewed Through MicroscopeEach diatom cell is surrounded by a cell wall known as a frustule. The frustule is made of silica. It has two halves that overlap.

Diatoms reproduce by cell division. When the parent cell divides, each daughter cell gets one half of the frustule of the parent cell and then grows the other half.

The word diatom comes from the Greek words dia, which means "across", and tome, which means "cut". The name comes from the way the frustule cuts the diatom in half.

There are about 100,000 known living species of diatoms.

Diatoms come in many different shapes. They range in size from 10 millionths to 150 millionths of a meter.

When diatoms die, they form a type of sediment known as called diatomaceous ooze at the bottom of the water.

The oldest known diatom fossils are about 185 million years old.