Book excerpt: Given the success of Volume I of this Research Topic, we are pleased to announce the launch of Volume II of The Role of Dietary Interventions in The Regulation of Host-Microbe Interactions. Nowadays, emerging evidence indicates that targeted diet could be an important tool for fighting ageing and diseases via adjusting the intestinal microbial composition. Besides, probiotics and specific strains isolated from human gut microbiota can also directly regulate host health and disease. Gut microbiota breaks down and biotransforms dietary and host-derived components, and these end products as well as bacterial surface components or secretions not only support host growth, but also possess signalling functions on systemic immune and metabolic responses. Although metagenomics, metabolomics, proteomics and transcriptomics are widely used to explore the interactions among microbiota with environments, diets, and diseases, it is more important to identify the key bacteria by means of these genomics, and isolate the targeted bacteria via cultivating omics, further studying their biological characteristics, their impact on the host.