This book summarizes the latest research findings in the neurocircuitry of innate behaviors, covering major topics such as innate fear, aggression, feeding, reward, social interaction, parental care, spatial navigation, and sleep-wake regulation. For decades, humans have been fascinated by wild animals' instincts, like the annual two-thousand-mile migration of the monarch butterfly in North American, and the "imprint" behavior of newborn birds. Since these instincts are always displayed in stereotypical patterns in most individuals of a given species, the neural circuits processing such behaviors must be genetically hard-wired in the brain. Recently, with the development of modern techniques, including optogenetics, retrograde and anterograde virus tracing, and in vivo calcium imaging, researchers have been able to determine and dissect the specific neural circuits for many innate behaviors by selectively manipulating well-defined cell types in the brain. This book discusses recent advances in the investigation of the neural-circuit mechanisms underlying innate behaviors.