The importance of the gut-brain axis in maintaining homeostasis has long been appreciated. However,the past 15 yr have seen the emergence of the microbiota (the trillions of microorganisms withinand on our bodies) as one of the key regulators of gut-brain function and has led to the appreciationof the importance of a distinct microbiota-gut-brain axis.This axis is gaining ever more traction infields investigating the biological and physiological basis of psychiatric, neurodevelopmental, age-re-lated, and neurodegenerative disorders. The microbiota and the brain communicate with each other viavarious routes including the immune system, tryptophan metabolism, the vagus nerve and the entericnervous system, involving microbial metabolites such as short-chain fatty acids, branched chain aminoacids, and peptidoglycans. Many factors can influence microbiota composition in early life, includinginfection, mode of birth delivery, use of antibiotic medications, the nature of nutritional provision,environmental stressors, and host genetics. At the other extreme of life, microbial diversity diminisheswith aging. Stress, in particular, can significantly impact the microbiota-gut-brain axis at all stages of life.Much recent work has implicated the gut microbiota in many conditions including autism, anxiety,obesity, schizophrenia, Parkinson’s disease, and Alzheimer’s disease. Animal models have been para-mount in linking the regulation of fundamental neural processes, such as neurogenesis and myelination,to microbiome activation of microglia. Moreover, translational human studies are ongoing and willgreatly enhance the field. Future studies will focus on understanding the mechanisms underlying themicrobiota-gut-brain axis and attempt to elucidate microbial-based intervention and therapeutic strat-egies for neuropsychiatric disorders CLICK TO REVIEW