Abstract: We disclose methods of sorting or separating mixtures of living cells (e.g., eukaryotic, prokaryotic, mammalian, pathogenic, bacterial, viral, etc.). We perform our methods by activating cell-selective photophoric labels, which photosensitize and chemically reduce a photosensitive metal compound to form metal grains, particles or crystals. The metal adheres to the cells and forms the basis for sorting or separating different cell types. Photophoric labels may include chemiluminescent agents such as peroxidase enzymes activated with peroxidase substrates capable of luminescence. Photosensitive metal compounds may be present in a light-sensitive matrix or emulsion containing photosensitizable metal compounds, which form metal grains, particles or crystals upon exposure to a developer solution. Developer solutions are formulated to substantially allow living cells to remain viable after exposure to the developing solution.