Raman spectroscopy characterises molecular vibrations by means of inelastic light scattering (the Raman effect). The technique is complementary to Fourier Transform Infra-red Spectroscopy (FTIR) analysis, and unknown materials can be identified by comparison with reference spectra. Raman requires minimal sample preparation, and is amenable to liquid & solid samples, including some intractable by FTIR such as aqueous dispersions and carbons. Spectral features depend on detailed composition and structure, and information on crystalline phase, local strain and temperature can be obtained.

In Raman microscopy, the analysis area is determined by the focused laser spot size (typically ~1 micron diameter). The spatial distributions of selected species, the complete chemical fingerprint, or local strain or temperature, can then be mapped over a sample if required.