How the secret world of soil microbes helps keep carbon in the ground

The largest terrestrial carbon sink on earth is the planet's soil. One of the fears that many scientists have is that a warming planet will liberate significant portions of the soil's carbon, turning it into carbon dioxide (CO2) gas, and so further accelerate the pace of planetary warming. One of the key players in this story is the microbe: Invisible, and yet the predominant form of life on earth.