Algae are a large, diverse group of simple microorganisms that have lived on Earth for billions of years. Although we typically associate the term algae with the slimy green stuff that accumulates on the surface of a stagnant pond,seaweed and kelp are also member of the algae family. In the right situations, algae can be very useful to humans, and their potential as an energy source has received lots of attention over the past few years.