The PIEZO1 and PIEZO2 membrane proteins form uniquely structured calcium permeable nonselective cation channels dedicated to mechanical force sensing in eukaryotic cells. In this review of the scientific literature, we address PIEZOs in the heart. PIEZOs enable the formation of the aortic valve, cardiac vasculature, and pericardial drainage. In the established heart, they enable baroreceptor pressure sensing and reflex regulation of the heart rate and influence the heart's size and stiffness through roles in cardiac myocytes and cardiac fibroblasts. Therefore, mechanical force sensing by PIEZOs participates in normal cardiac development and function. There is also interest in PIEZOs in pathophysiology, when the structure and mechanical properties of the heart often change. Studies in rats and mice suggest that experimentally induced cardiac stress and injury cause PIEZO upregulation that is adverse. Similar changes may occur in human heart disease, creating potential for therapeutic benefit through PIEZO modulation. This is a productive, accelerating, and exciting new research topic with importance for our understanding of the heart and its diseases.