Researchers in Utah have found that the tap water you drink leaves a chemical signature in your hair strands. Different parts of the country have different isotopes (types) of hydrogen and oxygen molecules in their tap water, and these isotopes get stored in your hair.

So what, you ask? Well, this finding could be useful in criminal investigations. For example, if a man is accused of a robbery in Minnesota but insists he's been in Florida for the past eight months, a test of his hair molecules could reveal whether he's telling the truth. Chemist Jurian A. Hoogewerff summarizes: "If you're a criminal, shave."

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