Despite the recent advances in molecular medicine and health care, cardiovascular diseases are still the leading cause of morbidity and mortality throughout the world. In 2006, nearly every other death in Germany resulted from disease of the circulatory system, and congenital heart diseases are thought to account for a high number of stillbirths and spontaneous abortions. Remarkable progress in basic research over the past decades has improved our understanding of the molecular mechanisms that govern a cardiac fate and has helped to establish cell-based therapeutic approaches to improve the course of cardiovascular diseases.