Most people have a certain degree of depression on their heads, which is a normal physiological phenomenon. This depression is caused by the growth and development of the skull. Everyone's skull is different in shape, so the degree and position of depression will be different. Skull, also known as skull, is a very important part of human skeletal system, which constitutes the external framework of skull and protects the sensory organs of brain and head. The formation process of skull can be divided into three stages: soft skull, pharyngeal skull and membranous skull, which are composed of many bones, which are connected with each other through gaps and joints. The shape and size of skulls vary from species to species, but in humans, skulls consist of 22 bones, including skulls and facial skulls.