Introduction. The study of neuronal differentiation of human induced pluripotent stem cells (iPSCs) offers wide prospects for modeling and analyzing the pathogenesis of human neurodegenerative brain diseases, screening the drugs for efficacious treatment, and obtaining specific cell material for personalized neurotransplantation. was to examine the ultrastructural properties of iPSCs reprogrammed from healthy donor fibroblasts and differentiated into ventral mesencephalic neurons on day 7, 14 and 19 in vitro. . We used a previously obtained iPSC cell line from a healthy donor. Cell differentiation was performed according to a previously designed protocol with modifications. Ultrathin sections (50–70 nm) of cultures embedded in Epon were contrasted with uranyl acetate and lead citrate, and then examined with the JEOL JEM-1011 transmission electron microscope (Japan). . By day 19 in vitro, the study material contained cells, most of which were very similar in their fine structure to mature neurons: they contained the Golgi apparatus and emerging Nissl bodies, and had formed various junctions with each other, including symmetric, asymmetric and mixed avesicular contacts, which preceded the formation of mature chemical synapses. An important ultrastructural criterion for synaptic development and maturation was the appearance of large granular vesicles, corresponding to “transport packages” necessary for the construction of the synaptic active zone and involving in the formation and differentiation of both postsynaptic and presynaptic structures. s. Our results suggest that ultrastructural changes in iPSCs differentiable into neurons, in the early stages of cultivation, reproduce the changes observed in early embryogenesis of the human brain, with their cellular composition resembling a neural tube containing mitotic neuroepithelial cells, radial glia, and maturing neurons. In the future, ultrastructural study of changes in iPSCs development, obtained from patients and undergoing neuronal differentiation after genome editing, will allow us to morphologically assess the degree of genetic defect elimination in transplantable cells.