Cyanobacteria have played an astoundingly fundamental role in shaping life on Earth today. Over a billion years ago, they oxygenated Earth's atmosphere. Cyanobacteria are also believed to have innovated photosynthesis and multicellularity. These photosynthesizing bacteria are found in many environments, including freshwater ecosystems. This episode was made in collaboration with Jared Leadbetter PhD at the California Institute of Technology.