Spermatogenesis is a tightly regulated cellular renovation and differentiation process. It consists of self-renewal and differentiation of spermatogonial stem cells (SSCs), spermatocytic meiosis and spermiogenesis; each of these processes is essential to the continuous, successful production of male gametes. During spermiogenesis, haploid spermatids undergo extensive cellular, molecular and morphological changes, including acrosome biogenesis, flagellum development, cytoplasmic reorganization and chromatin condensation. These changes ultimately result in mature spermatozoa with an acrosome-covered head and motile tail. In this book, Chapter One summarizes the progress that has been made in understanding the molecular mechanisms underlying acrosome biogenesis, and the authors discuss the potential directions of future investigations of this process. Chapter Two briefly addresses the basics of spermatogenesis and the synthesis of ncRNAs, and then the authors discuss the recent progress in understanding of the functions of miRNAs, endo-siRNAs, piRNAs and lncRNAs in the regulation of spermatogenesis. Chapter Three provides a review of the current literature on testicular immunoregulation and its underlying mechanisms, along with its effect on testicular functions.