New review: How chemical reactions can be used to build computing systems A single molecule contains a wealth of information. It includes not only the number of each kind of constituent atom, but also how they're arranged and how they attach to each other. And during chemical reactions, that information determines the outcome and becomes transformed. Molecules collide, break apart, reassemble, and rebuild in predictable ways. There's another way of looking at a chemical reaction, says Santa Fe Institute External Professor Juan-Pérez Mercader, who is a physicist and astrobiologist based at Harvard University. It's a kind of computation. A computing device is one that takes information as its input, then mechanically transforms that information and produces some output with a functional purpose. The input and output can be almost anything: Numbers, letters, objects, images, symbols, or something else.