Organoids capable of forming tissue-like structures have transformed the ability to model human development and disease. With the notable exception of the human heart, lineage-specific self-organizing organoids have been reported for all major organs. Researchers at the Institute of Molecular Biotechnology of the Austrian Academy of Sciences have developed the most realistic cardiac organoids. They established self-organizing cardioids from human pluripotent stem cells that intrinsically specify, pattern, and morph into chamber-like structures containing a cavity. According to their investigation, cardioid complexity can be controlled by signaling that instructs the separation of cardiomyocyte and endothelial layers and by directing epicardial spreading, inward migration, and differentiation. The results of this study which has been published in the journal Cell show that human cardioids represent a powerful platform to mechanistically dissect self-organization, congenital heart defects and serve as a foundation for future translational research.