The heart is the first organ to form and function in the embryo, and all subsequent events of life depend on its uninterrupted second-to-second contractions. Abnormalities in heart development result in congenital heart disease, the most frequent form of birth defect. Diseases of the adult heart represent the most prevalent cause of morbidity and mortality in the industrialized world. In this lecture, Eric Olson, Ph.D., will discuss some of the discoveries he and his colleagues have made, which have opened a new frontier in cardiovascular biology. His research on the genes that control heart development has provided a molecular blueprint for understanding how the heart forms and functions and has illuminated the fundamental principles of organ formation. Equally important is his demonstration that many of the same genes that control heart formation are called into play in the adult heart as a consequence of pathological stress.