A spermatozoon or spermatozoa (plural) refers to a motile sperm cell which is the male gamete. It is also called sperm cell. Sperm differentiation is a complicated series of morphological changes that occur in the seminiferous epithelium. Throughout this process, haploid round spermatids undergo significant structural and functional changes that result in highly polarized sperm. Development of new organelles, chromatin condensation and nuclear shaping, removal of residual cytoplasm, and assembly of the sperm flagella are significant changes that take place during the differentiation process. These events need the presence of a cytoskeleton, microtubules, actin filaments, and related motor and non-motor proteins, all of which deliver the vesicular and non-vesicular cargos to the proper intracellular locations. Spermatids have distinct protein trafficking systems that coordinate together to produce these changes. This book aims to shed light on some of the unexplored aspects of sperm differentiation mechanisms. It is a compilation of chapters that discuss the most vital concepts and emerging trends in this area of study. For all those who are interested in clinical reproductive medicine, this book can prove to be an essential guide.