Near-field Raman imaging is performed by holding a dielectric microsphere (e.g. of polystyrene) on or just above the surface of a sample in a Raman microscope. An illuminating laser beam is focused by the microsphere so as to produce a near-field interaction with the sample. Raman scattered light at shifted wavelengths is collected and analysed. The microsphere may be mounted on a cantilever of an atomic force microscope or other scanning probe microscope, which provides feedback to hold it in position relative to the sample surface. Alternatively, the microsphere may be held on the sample surface by an optical tweezer effect of the illuminating laser beam.