Imagine if the pullover you’re wearing automatically adapted itself to the temperature, warming you if you were shivering, or cooling you down if you were sweating. This means that the pullover would have to learn to recognize your discomfort and alter its properties so as to counter this discomfort. Other potential functionalities could include rapid drying or cushioning a fall. But how can such a pullover be created? What energy would it need? And where would it get it from? Complex calculations and a suitable energy source are necessary to fulfill all these functions.