The health of our skin - one of the body"s first lines of defense against illness and injury - depends upon the delicate balance between our own cells and the millions of bacteria and other one-celled microbes that live on its surface. To better understand this balance, National Institutes of Health researchers have set out to explore the skin"s microbiome, which is all of the DNA, or genomes, of all of the microbes that inhabit human skin. Their initial analysis, published in the journal Science, reveals that our skin is home to a much wider array of bacteria than previously thought.