Regenerative medicine is a challenging scientific field that aims to convert the pioneering knowledge of developmental biology and stem cell biology to clinical application. For patients with end-stage organ failure, organ transplantation is the only effective treatment; however, the paucity of organ for transplantation hinders the treatment of most patients. Therefore, regenerative medicine with transplantable organs has attracted attention. Our laboratory has established novel organoid culture technologies to reconstruct human organs from stem cells, including human induced pluripotent stem cells (iPSCs). We are currently developing a novel therapeutic strategy to substitute organ transplantation. Furthermore, we have applied our established technologies to cancer research and have reconstructed artificial refractory cancer tissue (cancer organoid) with tumor microenvironment. Based on this unique cancer organoid, we are currently developing a new drug-screening system to impede cancer relapse and metastasis.