A person's microbiota network is unique and first determined by their DNA. Microorganisms are initially seen by a person when an infant, in the birth canal after delivery, and in the mother's breast milk. The specific species of germs to which the newborn is exposed exclusively depends on the species present in the mother. Later, dietary changes and environmental exposures can alter a person's microbiome, either for the better or worse, regarding health and disease risk. The microbiome is made up of bacteria that can be both beneficial and detrimental. Most are symbiotic (beneficial to both the human body and the microbiota), and a tiny number are harmful (promoting disease). This book will touch on the following topic: Human physiology, health, and disease are all influenced by the microbiome. The microbiome is the most direct link between humans and their environment, primarily through nutrition. Dietary therapies that aim to alter host biology through altering the microbiome are currently being developed, and the market for these goods is booming.