Determining the biological bases for behavior, and the extent to which we can observe and explain their neural underpinnings, requires a bold, broadly defined research methodology. The interdisciplinary entries in this handbook are organized around the principle of "molecular psychology," which unites cutting-edge research from such wide-ranging disciplines as clinical neuroscience and genetics, psychology, behavioral neuroscience, and neuroethology. For the first time in a single volume, leaders in diverse research areas use molecular approaches to investigate social behavior, psychopathology, emotion, cognition and stress in healthy volunteers, patient populations, and an array of non-human species including rodents, insects, fish, and non-human primates. Chapters draw on molecular methods covering candidate genes, genome-wide association studies, copy number variations, gene expression studies, and epigenetics while addressing the ethical, legal, and social issues to emerge from this new and exciting research approach.