Did you know that there are quadrillions of germs in the world? And that hundreds of billions of germs may be in the room around you—and inside you as well? For readers 5 to 8, Seth Fishman explores the five main types of germs—bacteria, viruses, protozoa, fungi, and helminths—and the human immune system that protects us from them. Comical and stylish, Isabel Greenberg's illustrations somehow manage to make germs look rather endearing.