Rutter sets out in layman's terms what genetic science has discovered to date, explaining exactly what genes do, how much is nature and how much is nurture. He argues that nature and nurture are not truly separate, giving powerful illustrations of how the two interact to determine our behavior. He also considers the implications of genetic findings for policy and practice. This thought-provoking account will inform public debate about the implications of the Human Genome Project and, more broadly, the field of genetic science.