The photo-isomerization of azobenzene is a form of light-induced molecular motion. This isomerization can also lead to motion on larger length scales. For instance, polarized light will cause the molecules to isomerize and relax in random positions. However, those relaxed ("trans") molecules that fall perpendicular to the incoming light polarization will no longer be able to absorb, and will remain fixed. Thus, there is a statistical enrichment of chromophores perpendicular to polarized light (orientational hole burning). Polarized irradiation will make an azo-material anisotropic and therefore optically birefringent and dichroic. This photo-orientation can also be used to orient other materials (especially in liquid crystal systems).