In the study, the peculiarities of development in the embryonic and early pre-production periods of human ontogenesis are studied. The timing of the laying of structures from which gradually formed the atrium and ventricles of the heart, the interdermal and interventricular septum of the organ are established. The process of the formation of the valves of the heart has been observed. It was noted that in the prenatal of the 7th week of intrauterine development the structure of the heart resembles a definitive form. During the 4th week of intrauterine development on the upper wall the only atrium in the median line there is a concavity on the lower surface of which there is a crescentic protrusion, this is the initial of the primary atrial septum. In the 5 weeks of embryo, the free edge of the primary primitive partition grows caudally in the direction of the atrioventricular tubule, thus gradually separating the right and left atrium. In embryos 7-8 weeks of intrauterine development (embryos 18.0 - 30.0mm PСL), the heart takes the position from horizontal to vertical, due to intense and uneven growth adjacent organs and structures, especially the liver. In embrions of this age group, the length of the heart ranges from 1.5±0.05mm to 2.1±0.05mm, and the width at the base of the heart is – 480.0±10.0μm 590.0±5,0μm The thickness of the wall of the left ventricle is dominated by the thickness of the wall of the right ventricle at 30,0±2,0μm, and the thickness of the walls of the right and left atrium is almost the same.