Human genomics has revolutionized the practice of medicine and the very concepts of our health, well-being and longevity. Genes influence most of our characteristics, including the effectiveness of drug treatments, diets, cognitive therapies, and exercise. Harnessing the knowledge of genomics allows us to optimize preventive health measures. We can use the drug treatment that minimizes side effects and maximizes effectiveness when several alternatives are available. This book describes the basics of applying our 21st Century understanding of genetics and genomics to practical problems in medicine and disease prevention.