Baby at Week 6: The embryo is growing rapidly, although still tiny (about 2 millimeters long, roughly the size of a lentil). The head is disproportionately large compared to the body at this stage, a characteristic of early development. Tiny bumps are appearing on the embryo's body, marking the future locations of major body parts. The hands and feet are beginning to resemble paddles. Muscle fibers are starting to form, laying the groundwork for future movement. The baby's heart is now beating at almost twice the rate of your own! This tiny, rapid heartbeat is a powerful sign of the incredible life developing within you. Although you won't be able to feel them yet, the first movements of the baby begin this week. The embryo has the beginnings of a skeleton, although it's mostly cartilage at this point. Folds of tissue are developing that will eventually become your little one's chin, cheeks, and jaw. The areas that will become the eyes and nose are appearing as bumps, and the inner ear structure is pushing inward. The heart tube, which formed last week, continues to beat like a tiny drum. The kidneys and liver are also beginning to take shape, starting their crucial roles in filtering waste and other bodily functions. Limb buds are more noticeable now, and the mouth, jaw, and esophagus are forming.