This chapter traces the development of neuroscience from its early 17th seventeenth-century origins, to the 18th eighteenth- and 19th nineteenth-century perspectives on sensorimotor physiology and the electrical basis of neural function, to the 20th twentieth- and 21st twenty-first-century understandings of neurochemical and humoral communication. The neuroscience perspective intersected more and more with psychological and behavioral perspectives, as brain functional localization contributed insights into psychological processes such as language and emotion. This ultimately led to the establishment of behavioral neuroscience divisions in professional societies, such as the American Psychological Association in the early 20th twentieth century. Since thoese early beginnings, tremendous progress has been made in the development of behavioral neuroscience, in contrast to the prevailing behaviorism of the 1950s, neuroscience now is widely represented in all areas of psychology. A major conceptual historical trend in behavioral neuroscience is the evolution from unitary, simple explanatory concepts to the recognition that psychological processes are based on multiple complex interacting systems in neurobehavioral mechanisms, that extend across behavioral, physiological, endocrinological, cellular, and molecular domains. The ultimate understanding of psychological processes across broad levels of organization and analysis, from the behavioral to the cellular, remains a goal worth striving for.