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.