The developmental age of this part of the skeleton (fingers, palm, wrist) is the age of the child when compared with the bone age standard of the same part of the normal child. In the process of growth and development of children, due to the influence of many factors such as genetics, environment, nutrition, exercise and disease, the actual age of children often does not truly reflect the degree of individual maturity, while the level of skeletal development reflected by the bone age can express the role of genetic factors and the comprehensive influence of various environmental factors, and throughout the whole process of growth and development, can more truly reflect the maturity of children’s growth and development, therefore Therefore, it is a simple and credible indicator of children’s biological age, which is generally considered by the medical profession at present. The G-P atlas method of bone age assessment, short for Greulich-Pyle atlas method, was first published in 1950 and revised in 1959, then reprinted several times and has been used until now. The bone age was examined every 3 months until 1 year of age, every 6 months from 1 to 5 years of age, every year thereafter, and every 6 months during the puberty. Then grouped by sex and age, each group of X-ray films was lined up, one bone at a time, to obtain the sequence of increasing development of the bone. From each sequence, the plural or median film was selected as the representative film. This is illustrated with images and text. This method is based on children from better-off families in some western developed countries in the 1950s. Practical experience has shown that this age criterion is high and can introduce some bias in the diagnosis due to inconsistencies in the appearance and development of ossification centers. Although this method is the standard of bone age for our children, it is still widely used in some clinical fields that do not require high precision in bone age assessment, such as simple determination of whether a child’s skeletal development is significantly accelerated or delayed, because it is easy to use and the application of atlas makes it more comparable. 2.TW2 bone age assessment: In the early 1960s, Tanner and Whitehouse created a set of bone age scoring method, initially called TW1, modified in 1975 and renamed TW2, and reprinted in 1999 and renamed TW3. This method absorbs the latest growth and development data from Europe and the United States, and scores according to the emergence and morphological changes of 20 osteogenic centers in the wrist. Each osteogenic center is graded from emergence to maturity in 8-9 levels. The TW 2 bone age assessment method was used as follows: ① morphological staging and scoring of epiphysis according to bone age morphology; ② accumulation of points according to gender and morphological staging of bone age (RUS, CARP, T points); ③ tabulation of bone age according to gender and total points accumulated (RUS, CARP, T points), i.e. RUS, CARP, T age. CARP, T bone age. There are three sets of bone age data included: RUS bone age (assessing 13 tubular bones), CARP bone age (assessing 7 carpal bones), and T bone age, which is the sum of RUS bone age assessment method and CARP bone age assessment method, with a total of 20 bones (see Figure 1). TW3 considered T bone age to be of little significance and has eliminated this score. This method has the highest accuracy and is currently the most widely used method of bone age assessment internationally. It is suitable for longitudinal comparison of individuals or inter-individual comparison, as well as for relevant fields that require accurate assessment of bone age, such as evaluation of the degree of growth and development of children, assistance in the diagnosis of certain diseases affecting growth and development, prediction of height, and especially for guiding the clinical use and treatment of endocrine diseases in children. In addition, TW2 bone age and its TW2 adult height prediction system are considered to be more accurate in predicting adult height. However, this method is cumbersome and time-consuming to apply, and is much less convenient than the G-P bone age assessment method.