The book has been structured into chapters that serve as a guide for readers to gain a comprehensive understanding of various aspects of probiotics, starting from isolation to their usage and safety. It includes mechanisms of action, animal and human studies, and probiotic products available in the market, as well as functional roles of probiotics in human health by analyzing different intestinal disorders. The book emphasizes the ability of probiotics to modulate gut microbiota and the role of dietary management. It discusses advancements in the preparation of probiotic foods in the market, and in summary, provides an overview of fundamental concepts, mechanisms, therapeutic actions, technological aspects, and future research related to probiotic bacteria. This book will be beneficial for students, scientists, pharmacists, nutritionists, and professionals working in the field of gastrointestinal disorders and other diseases, as well as companies involved in the production of new functional foods or nutraceuticals. It is also useful for public health professionals and clinicians, as it successfully links food and health.