Normal fetal anatomy and development have been widely investigated with the development of various ultrasound fetal diagnoses, including estimation of gestational age, detection of fetal anomalies and evaluation of fetal growth. Our knowledge of fetal development, therefore, has been established through understanding of sectional images of the fetal body or organs obtained by two-dimensional ultrasound. Although three-dimensional ultrasound has been widely accepted for clinical use in antenatal care recently, a powerful tool of three-dimensional ultrasound has not yet been fully utilized. Recent advances of threedimensional ultrasound provide us with a distinct aspect of fetal anatomy and development. This chapter gives a clue to the entry into the new world of the fetus.