Adipose tissue is now recognized as a widely-dispersed secretory organ that plays a significant role in obesity. Ailhaud (U. de Nice-Sophia Antipolis, Nice, France) and a team of European and US laboratory experts and clinicians detail the classification, key techniques employed, and their potential problems, in the in vivo and in vitro study of brown and white fat tissues and cells from the nutritional, physiological, and molecular levels. Major treatment is accorded to the isolation, subcellular fractionation, and gene transfer into mature adipocytes, as well as metabolic aspects. Illustrations include microscopy study results, and a man wearing a portable detector for measuring adipose tissue blood flow.