The development of new research methods significantly changed our views on the role that the 3D organization of the genome plays in its functional activity. It was found that the genome is subdivided into structural-functional units that restrict the area of enhancer action at the level of spatial organization. Spatial reconfiguration of an extended genomic fragment was identified as a potential mechanism that activates or represses various genes. Accordingly, a distorted spatial organization of the genome often causes various diseases, including cancer. All these observations contributed to the emergence of 3D genomics as a new avenue of research. The review summarizes the most important discoveries in the field of 3D genomics and discusses the directions of its further development.