In medicine, an important indicator of skeletal development is length, which is related to the development of the three parts of the body: the skull, the spine, and the long bones. The development of the skull is together with the brain. Cranial development can be judged by the size of the head circumference, the cranial gap, and the lateness or early closure of the fontanel. For example, when a baby is born with an early fontanel closure, it is a sign that there may be a problem with the child’s cranial development. During the first year of life, the spine develops faster than the limbs, so appropriate exercises should be performed according to the development of the spine. For example, babies can hold their heads up in February to March, sit alone in June to July, and crawl in August to September. However, standing and sitting exercises should not be performed too early to avoid the formation of scoliosis. The long bones can be divided into three parts: diaphysis, epiphysis and metaphysis. During growth and development, the bones develop in the ossification centers at the ends of the long bones and in the epiphyseal cartilage plates. The development of the skull, long bones, and spine can be used to determine the length of the body, and thus the development of the human skeleton.