The digital textbook on gut microbiota and the microbiome covers a wide range of current topics that are central for clinical practice, research, and businesses. Emphasis is placed on modern approaches for the targeted manipulation of the intestinal microbiota , such as with genetically engineered microbial organisms, fecal microbiota transplantation (FMT) , and microbial ecosystem therapeutics (MET). The roles of probiotics, prebiotics, synbiotics, and postbiotics for health are also covered in detail – both for intestinal and extraintestinal diseases (based on preclinical and clinical studies). A particular focus is placed on illustrating the complex interactions along various microbiota-organ axes – especially the brain-gut-microbiome axis (gut-brain axis), gut-joint axis, gut-liver axis (GLA), gut-liver-brain axis, gut-liver-kidney axis, and gut-lung axis. The structured expertise is supported by artificial intelligence (AI) in a chat format, making the creation of presentations, scholarly publications, and dissertations efficient and user-friendly. Businesses also benefit from the textbook: it provides a solid knowledge database as a foundation for in-house research projects, marketing strategies, or the development of a proprietary microbiome database.