Sensations of hunger, thirst, sexual attraction, and love can dominate our thoughts to the exclusion of almost everything else, but until the last 10 years or so, the precise reasons why these passions arise have not been understood very well. We now know that these, and other drives like the urge to sleep, are controlled by a small portion of the brain called the hypothalamus. This book presents the latest information about how the brain controls our most basic drives. In a series of fascinating anecdotes, Young tells the tale of how scientists have discovered the role of the hypothalamus in our basic drives and in medical conditions in which these drives are drastically altered. Covering our need for food, water, sex, sleep, and other life essentials, he reveals the brain's part in how we provide for each, and how in some cases, those needs can swing wildly out of control resulting in problems such as obesity, diabetes, insomnia, or narcolepsy. He shows how regulating body temperature can affect the lifespan, how the aging process affects sexual behavior, how empathy and love develop in relationships with family members or with love interests, and how all these functions and more can go awry. Like other science writers before him, Young illuminates even the complex inner workings of the brain in a way that anyone can understand, so that readers are treated to a tour of a tiny part of the brain that is responsible for so many fundamental aspects of life.