Bone age, bone age, as the name suggests, is the age of the bones. We often hear doctors say, “Go get a bone age picture, see if you can still grow, see if you can still get growth hormone?” We often hear doctors say, “Go get a bone age picture to see if you can still grow, and if you can get growth hormone. Bone age really has such an important role, the following will follow the editor to explore the mystery of bone age. Human growth and development can be expressed in two “ages”, namely, life age (calendar age, CA) and biological age (bone age, BA). Clinically, X-ray films of the left wrist are often taken to observe the time and size of the ossification centers of the phalanges, carpal bones, and the lower ends of the radius and ulna, and to determine the actual degree of development of the skeleton, so as to determine the bone age, and most of the bone age films in China are read by the G-P method. Bone age is normal: BA-CA between -1~+1 years Bone age advancement: BA-CA ≥ 1 year Bone age lagging behind: BA-CA ≤ -1 year Bone age lagging behind: BA-CA ≤ -1 year Bone age assessment can more accurately reflect the level of growth and development and maturity, and early understanding of the child’s potential for growth and development and the trend of sexual maturity, predicting the adult height of children. The determination of bone age is also very helpful in the diagnosis of some pediatric endocrine diseases. Bone age advancement: precocious puberty, ovarian granulosa cell tumor, adrenal cortical hyperplasia or tumor, hyperthyroidism, simple obesity with rapid growth; Bone age lagging behind: growth hormone deficiency, Turner syndrome, hypothyroidism, cartilage insufficiency and so on, leading to obvious lagging behind in bone age. Don’t look down on a small bone age film, the role can not be underestimated. Clinical doctors will tell parents whether their children are suitable for growth hormone injections, whether there is a need for further examination, and can also predict the target height based on the condition of the bone age film. Some parents may be concerned that the bone age is an X-ray examination, which may cause radiation to the child. So does X-ray examination have any effect on children?X-ray is a kind of ionizing radiation, when irradiating the human body, it can produce biological effects on various cells and tissues of the body’s physical and chemical effects. However, for one bone age photo, the amount of X-ray is less than 0.00012 mSv. “Chinese children’s bone age scoring method” creator Prof. Ye Yiyan analogy: “a bone age photo of the amount of radiation, equivalent to 20 minutes in nature, flying 2 minutes, watching TV for 44 hours, eating for 21 days, minimal, no damage to the human body”. General fluoroscopy and radiography have little effect on the body because the exposure time is very short. It is only when too much X-ray exposure is received that the health of the body may be affected. Therefore, parents should not worry and go to the hospital as soon as possible for relevant examinations to clarify the cause of the disease and obtain the correct treatment.