Cytotoxicity at single cell level plays an important role in understanding biological mechanisms, detecting diseases, and screening therapeutics. Since cell populations are heterogeneous, differentiating individual cells in large populations become very important. This abstract reports a single cell array where the identity of each individual cell can be determined from coordinators assigned to the cell. Cytotoxicity upon X-ray radiation exposure and drug treatment are determined through reactive oxygen species (ROS) signal in cells and quantified by fluorescent intensity with MATLAB. This method can provide toxicities of over thousands of cells with superior statistics power after different treatment. The heterogeneity of cells in response to chemical and physical stimuli can be easily obtained to allow deep analysis of obtained toxicity data.