Microbiome Science, Nutrition & Probiotics is an interdisciplinary field that examines the structure and function of the complex microbial communities residing in the human body, particularly within the gastrointestinal tract, and their interaction with diet and health. The gut microbiome plays a fundamental role in digestion, nutrient metabolism, vitamin synthesis, immune system maturation, and protection against pathogens. Growing evidence also highlights its influence beyond the gut, including regulation of inflammation, metabolic health, and communication with the central nervous system through the gut–brain axis. Nutrition is a key driver of microbiome composition and activity. Diets rich in dietary fiber, whole grains, fruits, vegetables, legumes, and fermented foods promote microbial diversity and encourage the growth of beneficial bacteria that produce health-supporting metabolites such as short-chain fatty acids. Probiotics, defined as live microorganisms that confer health benefits when administered in adequate amounts, are increasingly used to support and restore gut microbial balance. Specific probiotic strains have demonstrated potential in improving digestive health, enhancing immune function, reducing antibiotic-associated complications, and supporting metabolic and mental well-being.