Final answer:
The brain stops growing in terms of size during early childhood, but it becomes more complex during adolescence.
Step-by-step explanation:
The brain does not increase in size very much during adolescence. Instead, most of the increase in brain size after birth occurs early in childhood. By the age of six, the brain has already attained about 90 percent of its adult size. The brain does, however, become significantly more complex during adolescence. In particular, the number of folds in the cerebral cortex of the brain increases. A process called "synaptic pruning" also occurs. In this process, unused pathways are eliminated. At the same time, myelination increases. Overall, the brain becomes more efficient and functional during adolescence, which in turn brings about major cognitive changes.