Hormones-such as estrogens, testosterone, thyroid hormones, and growth hormone-are essential for metabolic homeostasis in all cells. However, their levels decline with age, contributing to aging and chronic disease.  Proper hormone therapy can help delay the onset of age-related diseases, yet there is currently no authoritative, up-to-date resource on precision hormone optimization for healthy aging. Current standard of care textbooks rely on outdated concepts, while books aimed at non-specialist clinicians and patients are often written by non-experts and lack a solid scientific foundation. This book bridges that gap by presenting cutting-edge scientific data and insights from leading academic and private practice experts on the role of hormone optimization in healthy aging. It dispels common misconceptions about hormone therapy risks and highlights the proven benefits of precision hormone treatments. Drawing on both scientific evidence and clinical experience, it explores the distinctions between synthetic hormones and bioidentical, physiological hormones. Designed to challenge conventional thinking, this book aims to inspire discussion and further research among scientists and healthcare practitioners. It is an essential resource for basic and clinical researchers seeking translational knowledge on hormone therapy, as well as clinicians looking to integrate hormone optimization into their practice.