Embryology has been of interest to philosophers and scientists for over 2000 years, and a focus of intensive efforts for over 150. Despite this, our understanding of how the heart first forms and functions remains incomplete. Perhaps surprisingly, the basic concepts about how the early heart tube forms have changed completely over the past 20 years. Moreover, our views about how the cardiac muscle develops and matures, the valve and septa form and the heart muscle is vascularised have also changed radically over this period. Using the example of the arterial valves, that function to maintain unidirectional flow from the ventricles into the great arteries that carry blood to the lungs and to the rest of the body, I will illustrate some of these concepts. I will also describe how by understanding how the heart valves are made up of different types of progenitor cells, from different regions of the early embryo, this has relevance to the malformations that affect the valves and the diseases that they are predisposed to in later life.