In summary, this study demonstrates the utility of amino-substituted benzoselenadiazoles as small photosensitizers to kill metabolically-active cells in vitro and in vivo under full chemical and light control. Unlike in other current photosensitizers, the reduced size of benzoselenadiazoles retains key recognition properties of native metabolites and enables cell-selective uptake via various routes (e.g., peptidoglycan incorporation in bacteria, glucose transport in glioblastoma cells). This chemical approach opens new therapeutic avenues for the selective ablation of cells that do not present discriminatory cell surface markers, such as malignant cancer cells at early stages of disease, or that may become resistant to existing treatments, such as pathogenic bacteria. We also show that the dosing regime and light exposure required for photosensitive metabolites meet high safety standards and are compatible with current procedures used in clinical PDT. The possibility to ablate cells with high precision and purely because of differential or altered metabolism will enable mechanistic studies to identify unknown subsets of disease-causing cells and to develop safer therapeutic approaches with enhanced spatiotemporal resolution.