CARS - Coherent Anti-Stoke Raman Scattering is a growing microscopy technique where the vibrational energy between atoms in a molecule is used to visualize the specific molecule in the sample.

CARS is a coherent multiphoton process where lasers with 2 different wavelengths are used to probe the specific vibrational energy of the bond. What happens is that all the specific chemical bonds in the sample starts to vibrate coherently. They vibrate coherently and a resonancy is built up. When the laser light is scanned over the sample the CARS process occurs in the molecules that are excited. A blue shifted (higher energy) photon is emitted (the CARS photon) and due to that the photon is blue shifted most other photons can be filtered away and one can obtain a very high acurassy for the specific molecular vibration with a high signal to noise ratio.

The possibility to view specific molecular bonds in biological sample toghether with the advantages that a multi-photon process gives makes CARS a growing and very nice tool for bioimaging.