Chapter 9 will be useful for those who are wishing to master the field of three-dimensional free-radical copolymerization because it contains a general description of applicability of various methods used in analytical and physical chemistry for specific tasks: studying the kinetics and peculiarities of cross-linked polymers formation using the TFRP method.Conventional and widely known methods for high-molecular compound chemistry that are described in detail in scientific publications are inapplicable for threedimensional free-radical polymerization (TFRP) with formation of cross-linked polymers because the reaction medium is strongly structured, starting from small degrees of conversion (from the gel point), and produces polymers are nonfusible and insoluble. Therefore, this chapter gives a brief description of well-proven experimental methods used to study TFRP kinetics and the mechanism as well as the structure and properties of cross-linked polymers.