It was found that a layer of the nematic liquid crystalp‐N‐(p‐Methoxybenzylidene) aminon‐butylbenzen, extended on a triglycine sulfate crystal, takes on an orientational pattern which delineates the polarized domain structures. This technique quickly delineates domain structures in great detail and can be used on a wide variety of ferroelectric crystals. It is even applicable to a uniaxial regular type in which a domain structure cannot be detected by ordinary optical methods. The new method and the ordinary carbon powder pattern technique were compared on a triglycine sulfate crystal.