This book provides a clear and accessible overview of endophytes and their significance across plant biology, human health, and biotechnology. It introduces the biology of bacterial and fungal endophytes and describes their long-established symbiotic interactions with plants. Emphasis is placed on their contributions to plant growth, nutrient uptake, stress tolerance, and resistance to pathogens. The volume outlines current insights into the diverse secondary metabolites produced by endophytes, many of which exhibit antimicrobial, antifungal, anticancer, or immunomodulatory activities. These characteristics highlight their growing relevance for pharmaceutical research, including the development of new antibiotics and therapeutic agents. Additional chapters address emerging applications in dermatology, probiotic development, and microbiome studies. In agricultural settings, endophytes serve as effective biostimulants and biocontrol agents, offering environmentally sustainable alternatives to synthetic agrochemicals. Their ability to enhance plant resilience makes them an important component of future crop production strategies. The book also explores the expanding role of endophytes in industrial and environmental biotechnology. Their capacity to degrade pollutants, support bioremediation processes, and contribute to the production of biofuels, bioplastics, and other bio-based materials underscores their broad technological potential. Providing an interdisciplinary and up-to-date perspective, this volume is intended for researchers, academics, students and industry professionals in biotechnology-related fields. It offers a concise yet comprehensive introduction to the diverse applications and future possibilities of endophyte research.