I present a brief introduction to epigenetics, focused primarily on methylation of the genome and various regulatory RNAs, modifications of associated histones, and their importance in enabling us to adapt to real and changing environmental, developmental, and social circumstances. Following this is a more extensive overview of how it impacts our inheritance, our entire life (which changes as we age), and how we interact with others. Throughout, I emphasize the critical influence that stress, of many varieties exerts, via epigenetic means, on much of how we live and survive, mostly in the brain. I end with a short section on multigenerational transmission, drugs, and the importance of both social life and early life experiences in the development of adult diseases. There will be nothing about cancer. Although epigenetics is critical in that field, it is a whole different cobweb of complications (some involving stress). This review focuses on the impact of stress of many kinds on human physiology. It discusses DNA and histone modifications and regulation by various forms of RNA. It ends with a critical analysis of the impact of drugs and social interactions on the individual and transgenerational inheritance.