Final answer:
Adolescence is the term for the stage where children transition to becoming adults, involving significant physical, mental, and social changes starting from puberty.
Step-by-step explanation:
The stage in which children start to become adults physically and mentally is called adolescence. This period marks a significant transition between childhood and adulthood, characterized by a myriad of developmental milestones. Adolescence typically begins with puberty, the phase where there is rapid physical growth and sexual maturation occurs. This development phase also includes unparalleled cognitive growth, marked by a stronger sense of personal identity, and noticeable shifts in social relationships. It is important to note that there's another stage referred to as pre-adolescence, which is roughly the ages of 11 to 12 years where early signs of puberty might begin. Throughout adolescence, which generally spans the ages of 12 to 18 years, individuals undergo profound mental, emotional, and social changes in addition to the physical change.