Really. In Romeo and Juliet Shakespeare wrote:
O my love, my wife!
Death, that hath suck'd the honey of thy breath
Hath had no power yet upon thy beauty
That's a lovely, even heart-breaking, sentiment if you think about it. But I'm not so sure the Bard's breath smelled like honey or that he was at all beautiful when he died. Still, the odds are good that when you suck in a breath you're breathing a molecule that he sucked in (and exhaled) with his last breath.
Dartmouth College mathematics professor J. Laurie Snell did the math and says the odds are good--nearly 2 in 3--that some of your next inhalation was part of the 16th-century poet's final exhalation.
Snell assumed the total number of molecules in the atmosphere (1044) and the total number of molecules in the average breath (1022) and performed a series of calculations to determine the probabilities. Even if you include only chemically stable nitrogen molecules in Shakespeare's final snort, the odds are better than 50-50 you're sharing his breath right now.
Which also means that you're probably breathing a used Atilla the Hun molecule too. And you know how advanced dentistry and oral hygiene were in those days.