This probably comes under the heading of things I'd be better off not knowing.
The little horror creature on top, scanned from the latest issue of Discover magazine, is e-coli, the little devil that makes people sick, even kills 'em, when food is contaminated. Honest to god, it looks like it comes from Hollywood special effects, but it's a real monster, folks. And while small, we should all fear this killer.
These other little critters are dust mites, who live their lives in our beds, munching on the dead skin cells we're constantly shedding. I have known about these little beasties, but try not to think about them when crawling into the rack for a night's z's. The idea that thousands of things are living off our leavings is unnerving to say the least. Good things these things are so small they can only be detected with very powerful microscopes. I can't even imagine what it would be like if they were big enough to see with the naked eye. To throw back the covers and see several thousand dead skin gourmands the size of black widows or cockroaches is more than the human mind can manage.