The present book is an attempt to explore the potential of fungal endophytes. It enables its readers to get acquainted with the recent updates on this subject. In the present book efforts were made to introduce the concept of endophytes, to describes the origin of endophytes, to discuss the major groups of endophytic fungi, to highlight the diversity & distribution of endophytic fungi, to brief the insights of the tissue, organ and host specificity in fungal endophytes, to describes the endophytic fungi and host plant relationship, to emphasize the importance of the endophytes. This book served as the first of its kind and will attract the attention of the people working in this area across the globe.