Electron microscopy, X-ray diffraction, and polarization microscopy are three powerful and complementary tools in ultrastructure research. The potentialities of both electron microscopy and polarization microscopy are considerably increased when combined with histochemistry. While electron-microscopic histochemical methods are widely used, the application of relevant histochemical reactions for polarization microscopic investigations is more scarce. This may be due to at least three things: (1) they are not sufficiently known; (2) the ultrastructural analysis based on these techniques is an indirect — and not always simple — approach which has, therefore, less popularity and credit among some scientists; (3) occasional abuse may cause distrust of this technique. The aim of this chapter is to sum up some theoretical aspects of histochemical reactions used in polarization microscopic ultrastructural analysis. The methods are described in Chapter 12.