In polarization microscopy the sample is observed between two crossed polarizers. For isotropic systems the direction of polarisation of the incident light is unchanged and the material between crossed polarisers appears always black during rotation of the stage. Anisotropic materials with an arbitrary orientation of the sample to the incident light appear colourful and show a periodical variation of the intensity of the colour rotating the stage. Colloidal crystals fulfilling the Bragg condition are optical anisotropic and can easily identified by polarization microscopy. This allows to indentify individual crystals by color. Polarization microscopy is a powerful tool to determine the crystallization/melting kinetics and the morphology of polycrystals.
