In the past thirty years, significant advances have been made in the field of reproductive biology in unlocking the molecular and biochemical events that regulate spermatogenesis in the mammalian testis. It was possible because of the unprecedented breakthroughs in molecular biology, cell biology, immunology, and biochemistry. I am fortunate to have personally witnessed such rapid changes in the field since I was a graduate student and a postdoctoral fellow in the late ’70s through the early ’80s. In this book entitled, Molecular Mechanisms in Spermatogenesis, I have included a collection of chapters written by colleagues on the latest development in the field using genomic and proteomic approaches to study spermatogenesis, as well as different mechanisms and/or molecules including environmental toxicants and transcription factors that regulate and/or affect spermatogenesis. The book begins with a chapter that provides the basic concept of cellular regulation of spermatogenesis. A few chapters are also dedicated to some of the latest findings on the Sertoli cell cytoskeleton and other molecules (e. g. , proteases, adhesion proteins) that regulate spermatogenesis. These chapters contain thought-provoking discussions and concepts which shall be welcomed by investigators in the field. It is obvious that many of these concepts will be updated and some may be amended in the years to come. However, they will serve as a guide and the basis for investigation by scientists in the field. Due to the page limit, I could not cover all areas of interest in this monograph; instead, I tried to present this subject area with a balanced approach. I hope this book will be helpful to young investigators who consider entering reproductive biology to get a balanced view of the latest developments in the field. For established investigators, these chapters will be helpful for their studies in the laboratory. I am indebted to members of my laboratory who have provided insightful and critical discussion in the course of preparing this book. I am also grateful to all the staff at Landes Bioscience in particular Cynthia Conomos, Celeste Carlton, Kristen Shumaker, and Megan Klein, who have helped me to work on this book from its inception through publication. Furthermore, I am grateful to my colleagues who have taken their time and worked with me these past two years on their chapters amidst the intensive day-to-day routines in their teaching, administration, research, and writing manuscripts and grant applications. Finally, I also want to thank my former mentors and friends Drs. Wayne Bardin, Barry Boettcher, Neal Musto, Glen Gunsalus and Bruno Silvestrini for their critiques, help, encouragement, and discussion during my graduate student and postdoctoral years in their laboratories in different parts of the world, who have introduced me to the fascinating areas of research in reproductive biology, animal/pharmaceutical models, set up a high standard of quality research, and unknowingly shaped my scientific personality and my approach to science.