A fetus is the developing stage of a human baby that occurs after the embryonic stage, typically starting around the 9th week of pregnancy. During this time, the fetus grows rapidly, and its organs and systems begin to mature. This is a crucial period for development, as the fetus prepares for life outside the womb. Throughout the pregnancy, the fetus is nourished through the placenta, which connects it to the mother's bloodstream. The fetus can respond to sounds and light, and by the end of the pregnancy, it is usually ready for birth, marking the transition from the womb to the outside world.