Аннотация:Polymer crystallization is one of the classical areas of polymer physics and also a very important topic in terms of practical applications in everyday life. Despite the fact that an enormous body of data has been acquired during about seven decades of extensive studies in this field, a complete understanding of the molecular mechanisms involved in the process of polymer crystallization is essentially lacking to date. The chapter introduces the main notions of the field such as the folded crystalline lamella and the hierarchical semicrystalline structure and describes some of the experimental approaches to study the kinetics and thermodynamics of polymer crystallization. It is shown how the recent techniques of variable-temperature atomic force microscopy and real-time synchrotron X-ray scattering and microfocus X-ray diffraction can allow the long-standing issues related to the crystalline lamellar arrangement and crystallization mechanisms to be addressed. In particular, the physical properties of semirigid chain polymers are described in some detail because this class of polymers exhibits an interesting interplay between the dynamics and structure of the crystalline and amorphous regions of the semicrystalline structure allowing their complex physics to be appreciated.