 The gut microbiota brain axis is a complex system that affects the brain's physiological, behavioral and cognitive functions through various communication routes, including neural networks, neuroendocrine systems and barrier paths. While its precise mechanism has not yet been fully understood, the microbiome can be used to define the composition and functional characteristics of gut microbiota and metagenomics is an appropriate technique to characterize it. The gut microbiota brain axis may provide a new way to protect the brain in the near future. This article was authored by Hongxing Wang and Yuping Wang.