On Oxygen: From Air to Tissues, the latest release in the Fundamentals of Physiology series, provides a fundamental overview of the entire oxygen pathway, sharing key mechanistic insights into the alternating conductive and diffusive steps of O2 transport. The book describes specific aspects along each stage of the oxygen route through the body, from the transfer of air to the alveoli, through the lungs, to the ultimate fate of O2 in the mitochondria. Additionally, the effect of specific disease states, aging, and developmental aspects are considered. This book, published in association with the International Union of Physiological Sciences, acts is a valuable introduction to the full biological journey of oxygen, and is a beneficial guide for students and researchers in physiology, sport science, pulmonology, and related fields.