This excerpt from "Inside the Teenage Brain" offers a glimpse into the research of Dr. Jay Giedd, a top neuroscientist who's studying the adolescent brain. Giedd uses magnetic imaging technology to peer into what he calls "the black box" of teenagers' brains. He's discovered an unexpected growth spurt, just before puberty, in the frontal cortex (the area of the brain involved in judgment, planning, and strategizing). This new growth is followed by a period of pruning and organizing the new neural connections which continues through adolescence.