"Pretend that a single glucose molecule (the basic sugar that our body metabolizes for energy) is a lego. If I wanted to store all my legos, I could keep them loosely in a box. However, the body likes to be neat so instead of just tossing them in there, our body will connect the legos into stacks (polymerization) for storage in order to save space as well as keep them separate from the free legos which I want to use for energy immediately."