Oxygen is historically entwined from its discovery with radical applications as a panacea by charlatans and by daring men constructing bridges using underwater caissons. Oxygen has made possible the exploration of the depths of the oceans beginning with hard-hat diving suits and extending to scuba gear, underwater habitats and submarines as well as space exploration. Molecular oxygen is critically involved in health and disease in more ways than any other element. It is essential for metabolism of food to nourish our bodies. Understanding its biological and chemical nature helps us to understand the effects of exercise, vitamins and supplements, and drugs used for cancer therapies. Oxygen, the Breath of Life is a comprehensive reference on the historical, biological, chemical and medical aspects of oxygen. Readers, both laymen and experts, will gain knowledge of the basics of oxygen chemistry, how it functions in the human body, the role of oxidants in the development of various diseases. Chapters contain historical notes which highlight the discoveries of pioneering researchers.