The first application of the pump–probe technique in biology was in vitro imaging of stimulated emission of a dye-labelled cell. Pump–probe imaging is now widely used for melanin imaging to differentiate between the two main forms of melanin eumelanin (brown/black) and pheomelanin (red/yellow). In melanoma, eumelanin is substantially increased. Therefore, imaging the distribution of eumelanin and pheomelanin can help to distinguish benign lesions and melanoma with high sensitivity