Human pluripotent stem cells can be differentiated into many different cell types, including cardiomyocytes (hPSC-CMs) that are potentially valuable resources for cardiac regenerative medicine and experimental models of the human cardiac tissue. We are interested in studying the electrophysiology of these derived cardiomyocytes in a variety of in vitro culture models, including spontaneously formed cell aggregates (human embryoid bodies, hEBs) and monolayers. Using optical mapping, we record high spatial resolution maps of action potentials and calcium transients from hPSC-CM populations, and study the heterogeneity in electrophysiology among these derived cardiomyocytes. We are working with other labs to develop automated algorithms to analyze action potential shapes by machine learning techniques that can