There has been a recent increase of interest in the research on the relationship of numerous neurological disorders and the variety of gut microbiota. Findings suggest the broad role of gut microbiota in modulation of several physiological and pathological phenomena. The fact that a bidirectional communication between gut microbiota and brain is necessary to maintain homeostasis is now well established. The components of the brain-gut-microbiota axis include the central nervous system (CNS), the neuroendocrine and immune systems, autonomic nervous system, enteric nervous system, and intestinal microbiota. Early life microbiota composition can be influenced by a variety of factors, including infection, delivery method, usage of antibiotics, type of nutrition, environmental stresses, and genetics. With age, microbial diversity decreases. At all stages of life, stress in particular has a profound effect on the microbiota-gut-brain axis.