Microbiome. Conceptual image of the human microbiome. Coloured scanning electron micrograph (SEM) of bacteria superimposed on the body. The Human Microbiome is the collection of microorganisms living in association with the human body. Bacteria in an average human body number ten times more than human cells. These microbes are generally not harmful to us, but are essential for maintaining health. They produce some vitamins that we do not have the genes to make, break down our food to extract nutrients, teach our immune systems how to recognize dangerous invaders and produce helpful anti-inflammatory compounds that fight disease-causing microbes. Changes in the composition of our microbiomes correlate with numerous disease states, raising the possibility that these communities could be used to treat disease.