Book excerpt: Since its conception, Understanding Human Sexuality has achieved distinction and success by following the science of human sexuality. The first of the modern sexuality textbooks, Understanding Human Sexuality introduced this topic to students through the science that has uncovered what we know about the field. Groundbreaking when it first appeared, this research-based tradition continues to result in a contemporary, balanced introduction to human sexuality in an integrated learning system that engages students in learning the content of the course, about others, and about themselves.