 The gut microbiota brain axis is a two-way communication system between the gut microbiota and the brain. This system can influence both physical and mental health, as it involves the gut brain neural network, neuroendocrine hypothalamic pituitary adrenal, HPA, axis, gut immune system, neurotransmitter production, and the intestinal mucosa and blood brain barriers. Research suggests that gut microbiota can affect the brain's functioning via these pathways, and that changes in the gut microbiota can lead to changes in the brain's structure and function. This article was authored by Hongxing Wang and Yuping Wang.