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.