The concept of epigenetics is fascinating, confusing, and often misapplied. Yet it offers the tantalizing promise of explaining how cells with the same DNA acquire different identities and behaviors as they develop, how traits may possibly be passed through generations without changes to DNA sequence, and how environmental exposure may influence biological functions and ultimately human health. In this book's wide-ranging, iconoclastic exploration of the topic, John Greally traces the evolution of the concept of epigenetics from its historical roots in embryology to today's sprawling landscape of molecular definitions, genomic technologies, and disease hypotheses. He shows how epigenetics has captivated scientists, clinicians, and the public-and why caution is needed to avoid overinterpretation and pseudoscience. Written with clarity and authority, Epigenetics rejects simplistic answers and exaggerated claims to refocus the reader on what matters most: how cells establish and preserve identity and how this understanding translates into insights that are meaningful for human health. Essential reading for scientists, clinicians, students, and anyone curious about biology, this book is a guide to what epigenetics is, and is not.