TOPIC:The concepts and research that underpin our understanding of how the brain is the organ of the mind. PURPOSE:To describe the dynamic nature of nervous system functioning and development; to discuss how the nervous system changes anatomically throughout the lifespan; to examine the vital role and interaction of genetics and environment; and to discuss the relationship among the brain, neurotransmission, genes, and psychiatric illness. SOURCES:Published literature. CONCLUSIONS:The latest research from the neurosciences lays to rest any suggestion that psychiatric illnesses are psychologically induced.