Due to individual differences, the possibility of continued growth at age 21 exists for both males and females. The age of 21 is at the end of puberty. The age range of puberty is generally defined as 10 to 20 years of age, which is the golden period of transition from childhood to adulthood. Due to the complex endocrine changes involved in this period, it is not only a stage of maturation of the reproductive system, but also a peak period of physical growth and development. Physical growth and development accelerates again during this period and a second peak occurs. Due to individual differences, if a boy’s cartilage plate and epiphysis are not completely fused together at the end of puberty, there is still some room for growth of the long bones, and growth in height can be realized at this time. However, if the cartilage plate and epiphysis are completely closed at the age of 21, there is no room for growth of the long bones at this time, that is, they will not grow taller again. In order to ensure that a 21 year old boy can continue to grow, it is recommended that a physical examination be done to observe the gap between the cartilage plate and the epiphysis. If there is a gap, diet and exercise can be enhanced to ensure that there can be high quality growth in height.