Chemical science entered the scene in the 18th century, and burst into prominence in the 19th century. During the last decade, there has been increased interest in the assessment of body composition in physiological and nutritional research and in sports medicine. During the past 50 years interest in the gross composition, size, and shape of the human body has accelerated as a result of development and validation of densitometric, radiogrammetric, and radioisotopic techniques. The scientific community, in no small measure due to the scholarly leadership of Josef Brozek and Francis Moore, has become aware of quantitative procedures in health and disease which divide the body into chemical entities and anatomic components such as total body fat, water, blood volume, red cell mass, cellular water, extracellular water, and define lean body or "fat-free" mass and active metabolic structure of the body. Recent years have seen the development of tools that can be applied to the living, to conduct a "bloodless dissection" of the human body so as to construct what James Gamble called a chemical anatomy; to discover what happens during growth and aging; and to learn some of the consequences of disease and of altered nutrition. In our highly industrialized and automated society, obesity and cardiovascular deterioration are closely associated with inactivity, overnutrition, and compulsive emotional stresses. The study of body composition spans ＞ 100 y, and the term body composition is widely used. However, it is unclear what this branch of science represents and what exactly is meant by the term body composition. Body-composition research is a branch of human biology that has three interconnecting areas: body-composition levels and their organizational rules, measurement techniques, and biological factors that influence body composition. Information related to body composition is accumulating rapidly and is extending our knowledge of human biology. Most of this information is now categorized as technical or biological. Nearly every aspect of clinical nutrition, selected areas within many medical specialties, and components of exercise science are touched on by the study of body composition. In this article, I review some basic historical introduction and areas of body-composition research.