Plankton are tiny organisms that, in many cases, requires a microscope to see them. The word plankton comes from the Greek meaning "drifters." Many of them move by way of the currents, which is why they get the name "drifters." There are two general types of plankton: phytoplankton and zooplankton. Phytoplankton are the primary producers that make their own food through photosynthesis. Zooplankton are very weak swimmers that do not make their own food. They are primary consumers. Organisms that are classified as zooplankton are larval fish, crabs, copepods, and others. Both phytoplankton and zooplankton are vital to marine ecosystems all over the world.