The preceding chapters all deal with equilibrium thermodynamics. However, it is absolutely impossible to understand functioning systems, such as motors, batteries, and distillation columns, let alone living and growing organisms, solely based on equilibrium thermodynamics. From this point of view, all of these systems would more or less slowly settle into an equilibrium state characterized by a minimum of energy and a maximum of entropy and remain there forever. The fact that such systems instead are able to generate, during extended periods of time, mechanical or electrical power, low entropy streams of matter, or can even self-replicate shows that they must somehow be able to stay away from equilibrium for prolonged period of times. It is obvious that this ability is intrinsically linked to the fact that actively working systems are always open.