Kleiber's Law is a scientific law that explains why larger animals need more energy than smaller ones. It states that the amount of energy an animal needs is related to its size. Smaller animals need less energy to move and stay alive than bigger ones. For example, a mouse needs a lot less energy to stay alive than an elephant does. The energy is needed for things like keeping their body temperature stable, moving, and digesting food. By understanding Kleiber's Law, scientists can better predict how much energy different animals need to survive.