This eminent treatise elucidates the Dynamic Energy Budget theory that unifies the commonalities among organisms, as prescribed by the implications of energetics, and links different levels of biological organization. The theory presents simple mechanistic rules that describe the uptake and use of energy and nutrients and the consequences for physiological organization throughout an organism's life cycle. Kooijman covers living organisms in a single quantitative framework and tests the predictions against a variety of experimental results at a range of organizational levels. The theory provides a theoretical underpinning to the method of indirect calorimetry.