Embryo reconstruction by somatic cell nuclear transfer (SCNT) has been used to demonstrate that mammalian somatic cells can dedifferentiate into a totipotent nucleus when introduced into an oocyte. This process of dedifferentiation of somatic cells after nuclear transplantation is defined as nuclear reprogramming although this terminology gives little information on the molecular events that characterize this process. When planning on strategies for nuclear reprogramming by nuclear transfer (NT) one may suggest that converting the somatic nuclear configuration into an embryonic state is highly desirable so this may promote a succession of events similar to those occurring during early embryo development. In the following part of this overview we will discuss the results of many studies that have investigated different aspects of nuclear remodelling after SCNT.