 Sex is everywhere: TV, billboards, magazines, music videos, even textbooks and the Internet. But how much do teenagers really know? Four million teens contract a sexually transmitted disease each year; nearly a third of sexually active teenage girls have already been pregnant at least once; two-thirds of teenagers say their parents have never talked to them about where to get birth control. Gail Elizabeth Wyatt is a sex researcher author of the book "No More Clueless Sex." She says, "We need to grow up and be more responsible as adults, as Americans, who have so much information at hand, and yet we re so afraid of sex that we won t even teach our own children." When, where and HOW should parents talk with their kids about sex. Watch ... "Talking About Sex."