Cardiovascular diseases such as cardiac arrhythmias (e.g., ventricular fibrillation), contribute to a significant proportion of deaths. Fibrillation produces chaotic excitation waves in the heart muscle, whose biophysical and dynamical origin is a topic of current research aiming at novel therapies, like Low-Energy Anti-fibrillation Pacing (LEAP) or ablation methods. Measuring the spatio-temporal wave pattern is key for understanding their features and developing new control methods. Electrical waves and calcium concentration on the heart surface can be measured optically in a Langendorff perfusion setup with fluorescent dyes, although the image quality is still poor and only activity of the surface can be monitored. Accordingly, R5 based at MPI will develop new methods based on optoacoustic imaging, and machine learning for optogenetic experiments, which can provide new perspectives for optical (using light) arrhythmia control.