During the second decade of human life, the body and brain undergo a profound and complex transformation, with emotions and intellect changing as rapidly and unpredictably as weight and height. These changes can be baffling - to teenagers and to those around them alike - but adolescence plays an important evolutionary role in who we become as adults and there are hard scientific facts behind the spots, the smells, and the sexual experimentation, as well as the existential angst, the anger, and the irresistible attraction to all the things that are bad for you. In clear, engaging and amiable prose, David Bainbridge explains the strange and wonderful science of the teenage years. And tells us just exactly what teenagers are for.