They’re just germs to us, but scientists find microbes nothing short of miraculous — the keys to human health. In fact, the American Museum of Natural History is devoting an entire exhibit to bacteria, “The Secret World Inside You,” opening Saturday.

“Some bacteria are actually good for you. They’re the first line of defense against dangerous bacteria,” says the show’s co-curator, microbiologist Susan Perkins. “Where we once saw microbes as enemies to combat, we now understand that most are actually allies.”

Here are a few facts that may dazzle or disgust you. Or both.

1. You have more bacteria on one of your hands than there are people on this planet — more than 7 billion bacterial cells on each. And since our right and left hands do different things, they have different kinds of bacteria.

2. You’ll never dream what your pillowcase shares with your toilet seat. “They both touch cheeks,” Perkins explains, “and since both cheeks are slightly dry, they [harbor] similar bacteria.” That bacteria isn’t harmful, she adds.

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3. French-kissing gives you more than you bargained for, Perkins says: One 10-second round of tongue hockey is long enough to transfer 50 million microbes. “You’re not just swapping spit — you’re swapping bacteria.”

4. Your own mouth harbors 200 different species of bacteria, most of it harmless. But bacteria converts sugar into acid, which causes cavities, so drop that leftover Halloween candy.

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