Sex is everywhere in the modern world. But why is it so important to who we are? What shapes our sexuality and how does our sexuality shape us. What impact have feminism, religion, and HIV/AIDS had on our attitudes to sex? This Very Short Introduction examines these questions and more, exploring how sexual norms have changed throughout history, from self-castrating early Christians to modern-day born-again virgins, from sexual liberationists to lesbian separatists; and tackling the major controversies around sex and sexuality today: ideas on masculinity and feminity, paedophilia, gay politics, sex education, eugenics, and even the future of sex itself.