 They re stubborn, impulsive and paranoid. They take huge risks and have trouble planning ahead. In someone thirty years old, this behavior would be considered pathological. But in a teenager, it s normal. "You know, once, once individuals get to be age 16, 17 they look pretty much like they will when they re adults. But their brains don t," says Dr. Elizabeth Sowell, a brain researcher at the University of California, Los Angeles. She says that new imaging technology is offering a never-before look inside the teenage brain, and that what we see is revealing a lot about why teenagers act the ways that they do. The new science is forcing researchers to rewrite the textbooks, and in the process, they re rewriting the parenting books, too. We ve always known that launching a teenager into the adult world requires great patience, love and attention. But it also helps if parents UNDERSTAND. Watch ... "The Teenage Brain."