Compost bins are full of rotting organic matter, such as vegetable peelings, moldy fruit and grass clippings. Which microorganisms help this material to decompose (rot)?

Microorganisms are tiny life forms, so small that we need a microscope to see them. There are many types: bacteria, viruses and some kinds of fungi. Did you know that if you could weigh all the microorganisms on the Earth, they would weigh more than all other species combined?  Microorganisms are found in every environment on the planet - even in the stomachs of cows and your own intestines.