A cardiac organoid is an in vitro miniaturized and simplified heart model that contains multiple cell types and is differentiated from hiPSCs. This complex 3D cardiac structure can better resemble the native heart in terms of gene expression and physiological function compared with the traditional 2D cardiomyocytes. Based on the knowledge of developmental biology, our group has developed methods that generate vascularized cardiac organoids which can be further used for investigating heart diseases and drug-induced cardiotoxicity.