Book excerpt: This excellent book describes the roles of the suprachiasmatic nucleus (SCN) of the hypothalamus as a regulatory center of homeostatic mechanism and a circadian oscillator in mammals, including humans. The authors emphasize two important points based on their findings: 1) SCN plays a critical role in central regulation of energy metabolism through which a constant supply of glucose to the central nervous system (CNS) is well maintained; and 2) neurons responsible for the regulation of energy metabolism are located in the ventrolateral part of the SCN and receive retinal neural inputs through both the retinohypothalamic tract and the geniculohypothalamic tract. The authors then discuss the evolutionary importance of these points to the survival of mammals on earth. Other topics examined include the involvement of light in the regulation of neural activity of the autonomic nervous system through the retina and SCN, in addition to the relation of the SCN with regulations of other autonomic nerve functions, such as blood pressure and body temperature. Central Regulation of Energy Metabolism with Special Reference to Circadian Rhythm is important reading for researchers and students in neuroendocrinologists, neurobiologists, biochemists, endocrinologists, physiologists, chronobiologists, psychologists, pharmacologists, and others interested in the topic.