This is a story that gives new meaning to "The Little Engine That Could" in a profound way.One source explains:
In what is called the "Great Oxidation Event," something very little appeared that started making the earth habitable for us through photosynthesis. What happened? This:Cyanobacteria is responsible terraforming earth, transforming it from an iron-rich water world with a choking, impenetrable carbon-dioxide atmosphere to one with blue water and a clear oxygenated atmosphere. They also enlarged the coastlines of the nascent continents, called cratons. It took these little guys millions of years to accomplish this! Cyanobacteria is also very nutritious for human consumption. Where did cyanobacteria come from, being able to terraform a planet and provide humanity with nutrition? Humanity's best friend from the Creator.Footnotes:[1] The Event that Transformed Earth http://www.bbc.com/earth/story/20150701-the-origin-of-the-air-we-breathe