The human microbiome is composed of the microbes, as well as their genes and genomes, that live in and on the human body. Scientists are discovering just how important these resident microbes are to our health and well-being, particularly with respect to the roles they play in maintaining our immune systems, contributing to the digestion of our food, and acting as a first line of defense against pathogens. There are many diseases that may be the result of disturbed microbiomes; however, microbiome-based medical treatments and applications are on the horizon.