Energy is vital for life. In economic terms, it is the currency with which living things “purchase necessary goods and services”. Production, storage, and optimal use of energy are important processes for supporting the activities that sustain life. Many energy transactions that occur in living systems are chemical in nature. The sun is the primary source of energy. The leaves of green plants are the receptors and transducers of sunlight. Solar energy is captured by plants and conserved in chemical bonds of compounds such as glucose, fatty acids, starch, and glycogen. In the physical and natural worlds, from atomic to ecological levels, the acquisition and utilization of energy follows Maxwell’s laws of thermodynamics. Regarding the first law, the overall measure of energy in the Universe is constant: no more can be created nor can the existing amount be destroyed. It can, however, be converted from one form to another. According to the second law, the freely accessible energy of a system (the energy available to do work) decreases inexorably while entropy increases. Disorder (= chaos) is hence the unconstrained state of matter. Inasmuch as living systems are complex, highly organized, stable states of matter that not only maintain their integrity (though temporarily), but also refine themselves, it would appear on a casual glance that life “runs uphill in a downhill Universe”, i.e., it advances counter to the dissipation of energy. If that actually occurred, the second law of thermodynamics would be violated. Instead of jeopardizing life, however, the second law of thermodynamics de facto guarantees it. Unlike the closed thermostatic state of ordinary laboratory (controlled) chemical reactions, living systems are open thermodynamic states of matter that access energy from their immediate surroundings as well as the Universe at large. As long as energy is available to be shifted from its proximate environment into a living entity, the biotic part of the system can increase in organizational complexity while still advancing the increasing entropy of the system.