Over a billion years ago, tiny jewel-like cyanobacteria oxygenated earth's atmosphere. These single-cell organisms are the reason we have air to breathe. Cyanobacteria are also believed to be the precursors responsible for photosynthesis and multicellularity as a whole. Cyanobacteria are found in many environments, including freshwater ecosystems. This program was produced in collaboration with Jared Leadbetter, Professor of Environmental Microbiology at the California Institute of Technology.