The genetic material of all the microbes (bacteria, fungi, protozoa and viruses) that live in an ecosystem. In common use, “microbiome” is synonymous with “microbiota”—the collection of microorganisms (themselves) in the environment.

There’s a community of 38,000,000,000,000 (that’s 38 trillion) microorganisms, mostly bacteria, living in and on your body. The majority of them reside in your gastrointestinal tract, but many others live in diverse places like your mouth, your skin, and your armpits. They represent 50% of you by cell count. Collectively, the genes harbored in these trillions of microbial cells constitute your microbiome.

Altogether, it weighs about 3-5 pounds (about the same as your brain) and is now being considered by some a ‘lost organ’.

So where did your microbiome come from? You probably remember from sixth grade biology that you inherit your genes from your parents. But did you know that your mother passes you your microbiome too? The process of receiving these foundational microbes is called seeding. They colonize your gastrointestinal system at birth (through the vaginal canal, skin-to-skin contact, breastfeeding, and interacting with your surrounding environment) and form the foundation of your immune system, serving as the instructors of what’s dangerous and what’s not.

Scientists in the field are excited about the potential of the microbiome as another lens through which we program, sustain, and enhance health.