Greg Roza 
Gross Things Under Your Feet [PDF ebook] 

People rarely think about what’s under their feet. If they’re inside, it might be a rug or a wood floor. However, there’s more than meets the eye beneath our feet-dust mites, bacteria, and other disgusting things exist on those surfaces. Step outside, and there’s a whole world of bugs, worms, and other matter underfoot. Readers will never look at the bottom of their shoes the same way after they discover how gross, but amazing, the world is.