**1. Introduction**

The placental trophoblast gives examples of genome multiplication included in the program of their lifespan during embryogenesis [1–8]. The degree of ploidy varies between different trophoblastic cell lineages and among different mammalian species indicating that increase of chromosomes or gene copies is required for functional activity of the cell or is dictated by the lifestiyle of a species [3, 5, 9]. Besides euploidy, the trophoblast cells show aneuploidy examples that varies between different mammalian species and may reflect both differences in the genome structure and, again, requirements of species-specific way of life. Here we would like to match the above-mentioned genome peculiarities with the cell nucleus organization of the trophoblast cells that may underlie their specific functions.
