Developmental biology is the study of the process by which organisms grow and develop, and is closely related to Ontogeny. Modern developmental biology studies the genetic control of cell growth, differentiation and morphogenesis, which is the process that gives rise to tissues, organs and anatomy, but also regeneration and aging,.
The embryonic heart starts developing from two distinct vascular tubes of the embryo around day 19 of the embryo's existence, under the signals of genetic expression arrived from the surrounding cardiogenic region — the embryonic "cranium", lateral to the neural plate.
For the next 3 days the embryonic folding will push the endocardial tubes from the cardiogenic region to a midline position, inside the future thoracic region. Once the endocardial tubes have reached this midline position they fuse, initiating the development of the future endocardium. A primitive heart tube is formed.