After growing for 8 weeks (the 10th week of pregnancy), the embryo becomes known as a fetus. The legs, arms, and torso muscles have begun to exercise and the heart is beating strong. Little hands and feets are starting to suggest fingers and toes. All the tiny human organs are in place and ready to mature. Over the next several months the fetus will grow and refine its human features in preparation for the world outside the uterus.