Max Planck Institute for Dynamics and Self Organization 1 article published in JoVE Medicine Advanced Cardiac Rhythm Management by Applying Optogenetic Multi-Site Photostimulation in Murine Hearts Laura Diaz-Maue*1,2, Janna Steinebach*1, Michael Schwaerzle8,9, Stefan Luther1,3,4,6, Patrick Ruther8,9, Claudia Richter1,5,6,7 1Research Group Biomedical Physics, Max Planck Institute for Dynamics and Self-Organization, 2Research Electronics Department, Max Planck Institute for Dynamics and Self-Organization, 3Department of Pharmacology and Toxicology, University Medical Center Goettingen, 4Institute for Nonlinear Dynamics, Georg-August-University Goettingen, 5Department of Cardiology and Pneumology, University Medical Center Goettingen, 6German Center for Cardiovascular Research, DZHK e.V., partner site Goettingen, 7Laboratory Animal Science Unit, German Primate Center Leibniz Institute for Primate Research, 8Department of Microsystems Engineering (IMTEK), University of Freiburg, 9Cluster of Excellence BrainLinks-BrainTools, University of Freiburg This work reports a method for controlling the cardiac rhythm of intact murine hearts of transgenic channelrhodopsin-2 (ChR2) mice using local photostimulation with a micro-LED array and simultaneous optical mapping of epicardial membrane potential.