A clinical study on human-induced pluripotent stem cells (hiPSCs) is underway in the ophthalmic field, and patients with advanced heart failure will be among the next targets for cell transplantation with hiPSCs. Although many approaches for production of hiPSC-derived cardiac myocytes (hiPSC-CMs) have been developed, numerous hurdles must be overcome to achieve safe and effective cardiac regenerative therapy (CRT) . Heart transplantation is the ultimate treatment option for severe heart failure; however, donor organs for transplantation are limited. CRT with hiPSCs has been proposed as an alternative to heart transplantation. In Japan, an iPSC clinical study for age-related macular degeneration has been initiated. This clinical study was feasible because the indication only requires tens of thousands of cells and successful purification of iPSC-derived retinal pigment epithelium by a series of pick up and expand procedures. In contrast, even though >2 years have passed since then, clinical studies for other diseases, including Parkinson disease and spinal cord injury, have not yet been initiated because of the requirement of millions of cells and difficulty in efficient production of pure target cells. Severe heart failure will also be among the next targets. CRT with hiPSCs can be divided into 3 steps: differentiation of large numbers of hiPSC-CMs, elimination of residual human pluripotent stem cells (hPSCs) and purification of hiPSC-CMs, and transplantation of hiPSC-CMs. As several hundred million CMs are required for CRT, it is essential to establish an efficient method for production of pure hiPSC-CMs. 3-Dimensional or 2-dimensional cardiac differentiation systems using recombinant proteins or small molecules related to BMP (bone morphogenic protein) and WNT (Wnt/β catenin) signaling are well-established.1 Despite significant recent improvements in the efficiency of cardiac differentiation, it is not practical to prepare pure CMs without …