Despite the fact that we spend roughly a third of our lives asleep, science has still not been able to provide an answer as to why we and other animals sleep. While much of sleep physiology has been elucidated over years of scientific research, there has never been a thorough explanation of sleep that accounts for all of the observed sleep phenomena and uncovers sleeps primary purpose and why it evolved in the first place. Until now. The Neurotransmitter Theory of Sleep integrates concepts from multiple disciplines and various models and theories (both old and new) into one unified explanation of sleep. Similar to how Einsteins General Theory of Relativity shed new light on the concept of gravity and supplanted Newtons ideas of gravitation, this book describes sleep neurophysiology in a new light and proposes an explanation that accounts for all the phenomena that have yielded numerous, seemingly disparate theories and hypotheses regarding sleeps primary purpose. This book is where it all comes together.