The microbiome is the combination of all the microorganisms that live in or on the body, along with the “host” - the body itself. More casually, all the bacteria and yeasts that live on our skin, in our mouth, in our gut, in the vagina, in the nasal cavity, and other places are thought of as our microbiota, or “flora”. In most healthy women, the vaginal microbiome is dominated by one of a few species of Lactobacillus: L. crispatus, L. jensenii, L. gasseri, and L. iners. A woman’s vaginal microbiome interacts with her body’s immune system in ways we are just beginning to understand.