Voltage-gated Ca2+ channels (VGCCs) are important therapeutic targets for cardiovascular and neuropsychiatric disorders. The Zhou lab engineered novel classes of genetically encoded photoswitchable inhibitors (based on LOV2-photoswitches; shown within the heart shape) for VGCCs to control calcium signals (bubbles) and calcium-dependent biological activities in excitable cells. Ideally, this optogenetic device can be adapted to suppress cardiac arrhythmia (indicated by asterisks), thereby intervening atrial fibrillation by light.