Across the fields of science and medicine, especially since the mid-twentieth century, researchers have discovered that the human body is not “alone” – it lives in concert with trillions of microorganisms that exist inside and on the body, outnumbering human cells by 10 to 1. “Microbiome” (a combination of the words “microbe” and “biome”) refers to these bacteria, viruses, and fungi, as well as their activities in their environment. What is fascinating is that these microbes are not just along for the ride. Some of them, particularly bacteria, have been found to play an essential role in the health of their human host. For example, bacteria in the gastrointestinal tract enable the digestion of foods and absorption of nutrients that would otherwise not be possible. And research has found there is a “gut-brain axis”  – biochemical pathways going both ways between the gut and the brain to trigger chemical processes that affect health outcomes.