Human embryonic and fetal development stages refer to the process of growth and differentiation from conception to birth. It begins with fertilization, where a sperm cell and an egg combine to form a zygote. The embryonic stage lasts from weeks 1 to 8, during which the basic structures of the body, such as the heart, brain, and spinal cord, begin to form. By the end of this stage, the embryo has recognizable human features. The fetal stage begins at week 9 and continues until birth. During this stage, the body grows rapidly, organs become fully functional, and the fetus develops more complex systems, including the skeletal and muscular systems. Throughout both stages, the fetus is nourished and protected within the mother’s uterus until birth.