Let's get dense. If we take all the atoms inside you, all roughly 70,000,000,000,000,000,000,000,000,000 of them, and squeeze away all the space inside, then, says physicist Brian Greene:
That's a very tight fit. So tight that in real life, it couldn't happen. It's not physically possible. Atoms won't crunch that close. But people, it seems, are willing to try.