Microscopic Plants: Phytoplankton
Phytoplankton means “floating plants.” Over 90% of the worlds food (carbohydrates) come from phytoplankton. It is the single most important process for life and the production of food on Earth.
Types of phytoplankton include bacteria, protists, and single-celled plants. Primitive photosynthetic bacterial appear in the fossil record about 3 billion years ago. Their oxygen production is what made life possible for aerobic organisms (particularly animals) to evolve.