This richly illustrated book provides a detailed description of the gross anatomy, light microscopy, immunohistochemistry, and electron microscopy of the adipose organ, which comprises subcutaneous and visceral fat depots. Findings in mice of differing genetic backgrounds (obesity prone and resistant) and maintained in standard and various physiologic and pathologic conditions are presented. The latter conditions include chronic cold exposure, warm exposure, fasting, pregnancy lactation, and obesity. Features of the fetal adipose organ are described in a separate chapter, and results from transgenic mice are also presented when relevant. The human adipose organ is addressed in several chapters that include magnetic resonance and fetal findings. Most of the results regarding the adipose organ anatomy in different physiologic conditions are new, and the story of pink adipocytes (white-to-pink transdifferentiation) is quite innovative.