Adrian Bejan is a professor of mechanical engineering at Duke University who is particularly interested in how to make things more efficient. Not long ago, he discovered what he calls the constructal law in nature. This law basically says that for a flow system to persist in time, it must evolve to provide greater and better flow. For instance, a river basin changes over time to ensure that the water from one body flows more efficiently into the water of another body. It sounds simple, but it’s actually quite revolutionary. Adrian Bejan explains his theory and how it works in detail in his new book co-written with J. Peder Zane called, "Design in Nature, How the Constructal Law Governs Evolution in Biology, Physics, Technology, and Social Organization" (Random House/2012).