A teaspoon of sea water can hold a soupy serving of a million phytoplankton! Invisible to the naked eye, plant-like phytoplankton are the source of our atmosphere, our climate, our ocean food chain, much of our oil supply, and more. They're also food for zooplankton, tiny animals that often look like weird life forms from outer space. A great teacher reference and student reader for the fifth grade activity "The Great Plankton Race."