A microscopic imaging technique that takes advantage of the process of harmonic generation that occurs when photons interact to generate new photons of a different wavelength. In second harmonic generation, two photons of the same wavelength and frequency, such as from a LASER, interact inside a medium and are converted to a photon of twice the frequency and half of the wavelength of the two incident photons. The light signals captured are used to produce images that are dependent on the unique optical properties of the material.