Final answer:
Puberty marks the transition into adolescence with the development of secondary sexual characteristics, the adolescent growth spurt, and significant brain development, particularly in the prefrontal cortex.
Step-by-step explanation:
Puberty is a significant stage of life when a child transitions into sexual maturity, signaling the onset of adolescence. This period involves numerous physical changes, including the development of secondary sexual characteristics such as breast tissue in girls and external genital changes in boys. Girls generally begin puberty earlier than boys, with visible signs like breast development and pubic hair growth starting between the ages of nine and ten. Boys typically enter puberty around the ages of eleven and twelve, experiencing changes in their genitalia and pubic hair.
One of the hallmark events during this time is the adolescent growth spurt (AGS), characterized by rapid increases in height and weight. While brain size may not increase significantly during this period, there is considerable brain development, particularly in the prefrontal cortex, which impacts decision-making abilities and control over impulses. By around the age of fifteen, many adolescents possess cognitive abilities at levels similar to adults. Generally, an early or late start to puberty is considered normal, with children undergoing these changes at their own pace.