Final answer:
The brain reaches about 90 percent of its adult size by the age of six years, experiencing rapid growth in early childhood through neurogenesis and blooming, followed by synaptic pruning during adolescence.
Step-by-step explanation:
Neural tissues grow rapidly after birth, with the brain reaching near adult size by a specific age during childhood. By the age of six, the brain has already attained about 90 percent of its adult size. The early years are crucial as they involve neurogenesis and the formation of neural pathways, known as blooming, whereas the pruning and refining of connections happen later mainly through adolescence.
The process of myelination of nerves, which is essential for efficient nervous system functioning, starts before birth but is not completed until adolescence. The brain's development is also influenced by factors like sensory stimulation and nutrition. A healthy, well-nourished child will typically see a rapid progression in both physical and cognitive abilities during infancy and childhood.