INVISIBLE ALLIES is divided into five main chapters. “Microbes at the Table” is a detailed summary of the history of cheese and cheese production. You may or may not be surprised to know that there are scientists who are “cheese microbiologists” who study just how cheese is made by the microbes. “As an expert on cheese microbiology once said, looking for the activity of a particular microbe in a cheese is a bit like looking for the Loch Ness monster. On the scale of a microbe, the cheese is as big as the 600-foot-deep lake in Scotland—it offers many living creatures plenty of room to hide. Tools for microbial explorations invented in the last twenty years of the twentieth century improved our ability to find and distinguish microbes, and some of these tools are being used to explore the microbial wilderness that is cheese” (34). Likewise, “Our Daily Bread” is a detailed summary of how bread is made—specifically leavened bread. This chapter is devoted to the wonderful (yet diverse) microbe yeast. Included in this section is a “try this at home” experiment for making your own sour dough bread. In addition it chronicles the lives of the brothers Fleischmann and their yeast-selling company. “Food of the Gods” begins as a chapter devoted to the history of the cacao bean, which was thought by many cultures to be “the food of the gods” (in fact it was money!) Toward the end of the chapter, however, Farrell goes slightly off topic to present brief histories of cultural and ethnic foods from around the world that rely on microbes in their production. Included, for example, is a discussion of kimchee, soy sauce, cassava, sausage, and fermented fish. She also touches on the idea that these foods (along with cheese, bread, and chocolate) are an important part of our individual cultures. “Microbes Are Us” presents how the human body uses microbes (in the mouth, stomach, and intestines) to digest food. She stresses the point that these microbes in our bodies are crucial to making our human bodies function properly. We couldn’t live long without them. The final chapter “Rot Away” discusses how microbes are used to rid the world of human waste. Perhaps the grossest chapter, it discusses how microbes decompose poop—her words not mine—and dead people, plants, and animals.

INVISIBLE ALLIES is a fascinating book. Although she includes illustrations (photographs, sketches, drawings, etc.) they are all in black and white. But the text itself should be engaging enough to hold the attention span. The narrative style is informative yet at times slips into light conversation. Included are a glossary, index, and endnotes with selected bibliography. It is definitely an enjoyable read.