Size is a fundamental biological feature that impacts physiology of the cell. This means not only the overal cell size but also the size of its organelles (subcellular structures). The basic aspect of size is its absolute value, having the upper and lower limits that are necessary for functional requirements. The mammalian oocyt or early-cleavage stage embryo represents, according to our opinion, an excellent experimental model systém. The present project aims to explore some fundamental questions of size scaling in mammalian oocytes and early embryos (nukleus, necleoli, chfomosomes, etc.). As some micromanipulation approaches are commonly used in understanding of nucleo-cytoplasmic interactions, size scalling mechanisms and realtedd consequences will enhance the efficiency of them.