1, adipose tissue The growth of adipose tissue is mainly manifested by the increase in the number of adipocytes and the increase in volume. The number of adipocytes increases from the middle of the fetus to the peak at the end of the first year, and then increases at a decelerating rate. 2 to 15 years of age, the number of adipocytes increases about 5 times. The increase in adipocyte volume increases 1-fold from the late fetal period to birth, and then gradually decreases, with little change in adipocyte size from preschool to prepubertal period. When growth accelerates during adolescence, adipocyte volume increases again. The percentage of whole body adipose tissue to body weight is consistent with the growth rate: 16% of body weight at birth, increasing to 22% in the first year, then gradually decreasing to 12%-15% at age 5. At the second growth spurt in adolescence, there is a significant gender difference in this percentage, 24.6% for girls and 2 times more than for boys. Subcutaneous fat accounts for more than 50% of total body fat. Subcutaneous fat measurement not only reflects the amount of body fat, but also can indirectly determine the body composition, body density and the degree of obesity and malnutrition. In practice, the thickness of sebum is often measured in four parts: biceps, triceps, subscapularis and suprailiac. 2, the growth of muscle tissue fetal period muscle tissue growth is poor, after birth with the increase in activity gradually grow, basically parallel to the increase in weight. Children have finer muscle fibers and more interstitial tissue. After birth, muscle growth is mainly muscle fiber thickening, after the age of 5 years, then muscle growth is obvious, and there are gender differences. The proportion of muscle to body weight is significantly greater in boys than in girls. At birth, the muscle tone of infants is high, with the flexors of the limbs being the most important. With the development of the cerebral cortex, muscle tone gradually decreases after 1 to 2 months, generally upper limbs to 2 to 2.5 months of age, lower limbs 3 to 4 months of age muscle tone is normal, the limbs can be freely extended and flexed activities. Muscle growth is closely related to nutritional status, lifestyle, and amount of exercise. From a young age, infants are often allowed to perform passive or active exercises, such as lying down, turning over, crawling, walking, gymnastics, games, etc., which can promote the thickening of muscle fibers and the enhancement of muscle mobility and endurance. Muscle growth in children can be examined by observing the degree of flexibility in active movement and the degree of muscle resistance during passive movement, palpating the developed muscles, and grip strength. Abnormal muscle growth can be seen in conditions such as severe malnutrition and progressive muscular atrophy.