The anatomy and physiology of placental and embryonic development is a field where medicine exerts its impact on early pregnancy and opens fascinating aspects of embryonic differentiation. The introduction of high frequency transvaginal transducers as well as three and four dimensional sonography has resulted in remarkable progress in ultrasonic visualization of early embryos and fetuses.

Ultrasound has been widely used in the field of early human development due to its safety, diagnostic accuracy and convenience. Normal fetal anatomy and development have been widely investigated using two-dimensional ultrasound and most of the knowledge regarding early human development were established through understanding of sectional images of fetal body and organs obtained by two-dimensional ultrasound. Usage of new techniques has produced more objective and accurate information of embryonal and early fetal development. For the first time parallel analyses of structural and functional parameters in the first 12 weeks of gestation become possible. This article deals with establishment of human life from ovum and sperm, though fertilization, detailed histological development and the establishment of the placenta, and early human development visualized by 2- and 3-dimensional ultrasonography.