Heart failure plagues the developed world and kills more people than any other disease. This is usually caused by a shortage of specialized heart muscle cells known as cardiomyocytes, and powerful treatments that regenerate lost heart muscle could help millions of patients each year. is well documented in developing mammals, as well as in amphibians and fish. However, postnatal human heart regeneration is limited to the very slow replacement of cardiomyocytes. Several experimental strategies are underway to revascularize the injured heart using adult and pluripotent stem cells, cell reprogramming, and tissue engineering. Although many challenges remain, these interventions may ultimately lead to better approaches to treating or preventing heart failure.