The time period of secondary development refers to puberty, which is the period of gradual development from childhood to adult transition. Puberty is a critical period of rapid human development and the second growth spurt of life after infancy, when both boys and girls undergo tremendous and wonderful changes inside and outside their bodies. Generally the second developmental period of boys starts from 10-13 years old, there are also individual differences, so collectively it is called 10-20 years old development as the developmental stage of puberty, generally children start to develop puberty from 10-13 years old, which can be gradually extended to 20 years old. A child’s pubertal development gradually changes with age. For example, boys can experience changes in appearance, which can be marked by beard growth, prominent throat nodes, weight gain, and violent height growth. Along with these changes in appearance, there are also gradual changes in a boy’s sexual organs, which can show pubic hair growth, testicular growth, penis growth and thickening. Adolescent boys should wash their skin often, develop good hygiene habits, and pay attention to diet and nutrition. Boys’ sebaceous glands secrete a lot, use skin care products appropriately, ensure sufficient sleep, etc.