"Wherever you go, tiny hitchhikers tag along for the ride," this intriguing illustrated nonfiction book begins. "The hitchhikers are actually microbes --- tiny living things so small that you need a microscope to see them. And every person carries around trillions and trillions of these critters." Six of the most common "critters" that live in and on our bodies are introduced here: bacteria, archaea, viruses, fungi, protists and mites. Each one has...