NEXEL Co., Ltd. 1 article published in JoVE Medicine High-Throughput Optical Controlling and Recording Calcium Signal in iPSC-Derived Cardiomyocytes for Toxicity Testing and Phenotypic Drug Screening Yu-Fen Chang1, Wan-Chi Su1, Chih-Chuan Su1, Min-Wen Chung1, Jin Chang2, You-Yi Li3, Yi-Ju Kao3, Wen-Pin Chen3, Matthew J. Daniels4,5,6 1LumiSTAR Biotechnology, Inc., 2NEXEL Co., Ltd., 3Institute of Pharmacology, College of Medicine, National Taiwan University, 4Manchester Heart Centre, Manchester Royal Infirmary, Manchester University NHS Foundation Trust, 5Division of Cardiovascular Sciences, Manchester Academic Health Sciences Centre, University of Manchester, 6Division of Cell Matrix Biology and Regenerative Medicine, University of Manchester The present protocol describes all-optical control and observation of triggered cellular activity in iPSC-derived cardiomyocytes (iPSC-CMs) for high throughput drug screening and toxicity testing. Multi-parametric quantification of phenotypic patterns in time, and space, are shown. Long-term effects of drugs over hours, or sequential measurements over days, are demonstrated.