When does the growing brain begin to resemble the adult brain?

Neuroscientist mostly agreed that there is no agreed-on benchmark, that a brain is fully developed. However, it is safe to say that brain is continuing to developed well past at the age of "18". Brain development happen in different stages and all in varying times. Brain consist of gray matter and white matter. Gray matter grows as we learn, as puberty sets in, our brain starts to prune back some of the gray matter, and produces more white matter, to share information better and faster. Overall most neuroscientist agree that, there is no magic age at which the brain reaches adulthood, but about age 22 or 23, the brain is pretty much done developing.