The heart is the first functional organ in the human embryo and starts to beat by 4 weeks of development. Recently, progressive advances in medical ultrasonography, especially high-frequency transvaginal ultrasonography and the color Doppler equipment allow access to the developing embryonic human heart. The anatomical and functional characteristics of the embryonic heart are different from those of the fetus and neonate. Embryo crown-rump-length (CRL) at 2 mm shows a discernible heartbeat. At this time, the embryonic heart is in the cardiac tube stage. Embryo CRL at 5 mm shows distinct differential movements of the ventricles and atria (13th Carnegie stage, 6+4/7 gestational weeks). At the 7th gestational weeks, an interventricular septum can be visualized in the embryonic heart. Although a heartbeat can be detected and gross cardiac structures are visualized early in gestation, visualization of some embryologically important intracardiac structures, such as the endocardial cushion, atrioventricular foramen, or atrioventricular valves are still limited, even with the latest high-end equipment. Cine function and color Doppler provide some valuable information about the morphology and function of the developing embryonic heart. For the evaluation of the embryonic heart using ultrasonography, keep the principle of “As Low As Reasonably Achievable” (ALARA) and the least use of color Doppler and pulsed Doppler.