The human microbiome is complicated stuff: Researchers are still struggling to understand the trillions of microbes that call our bodies home—how we acquire them and how they affect everything from our digestion to our mood. It’s the subject of Ph.D. work and medical research, but in this lighthearted picture book, it also becomes whimsical learning for 8- to 12-year-olds. Using simple language (with sporadic pronunciation guides for potentially unfamiliar terms), the book presents the most current science on the unseen hitchhikers living all over and inside our bodies. Colorful, cartoony illustrations help break up the material, and sidebars with “Did you Know?” fun facts and microbe-themed jokes further lighten the educational load. (Some of the jokes land better than others: “How does a microbe call home? Using its cell phone” will probably elicit more eyerolls than laughs, even from the youngest readers.) Of course, any discussion about the human microbiome will inevitably involve poop, and the book doesn’t fail to deliver on that favorite childhood subject either: Readers will be especially delighted (and grossed out) by a quick section on the potential health benefits of fecal transplants. The microbiome is a difficult subject, but thanks to careful wording, microbe cartoons, and plenty of sidebar elements, in this book it becomes child’s play.