There’s nothing like finding a book that changes your mind. But more satisfying still is finding one that opens it—that pries apart your old synaptic connections and stuffs into those gaps ideas you might never have imagined otherwise. For me, Ed Yong’s I Contain Multitudes is such a book.

In this extraordinary debut, Yong—a lyrical, inventive, and deeply informed science writer for The Atlantic, and blogger for National Geographic—lifts the veil off a world that seems fantastical in scale: the trillions upon trillions of microbes that live within us, on us, and all around us. Yong is a literary van Leeuwenhoek, shining a makeshift microscope on this teeming realm of bacteria, viruses, protozoa, and other invisible organisms—mysterious beasts that van Leeuwenhoek, in the 17th century, called “animalcules.” And Yong reports each unusual symbiosis, each staggering statistic—“Every person aerosolizes around 37 million bacteria per hour”—with an infectious sense of marvel.

Among the mind-opening tales is that of Jack Gilbert and family, who spend much of their day swabbing not only themselves, but also their home’s light switches, doorknobs, walls, counters, and floors, in an attempt to catalog the multitudes of microbiota who squat rent-free in their house. But what’s truly striking is (a) how much this community changes from day to day, as friends come to visit or as the family dog shuttles in and out—in each case, leaving an “aura” of bacteria in their wake the way a badger or hyena leaves a telltale scent. And (b) how important this ever-adjusting diversity is to our well-being.

Indeed, a failure to understand the benefits of the typically benign, co-regulating microbial neighborhoods we live in (along with a general overriding fear of “germs”) may actually be contributing to the high rates of dangerous infection in hospitals—which lead to some 90,000 deaths a year by some reports. By rigorously disinfecting such environments could we be unwittingly creating a safe haven for the most deadly pathogens?

Gilbert is investigating this critical question and others. You see, when not home-swabbing, he’s a professor of surgery at the University of Chicago and group leader for microbial ecology at Argonne National Laboratory (where he leads a much, much larger effort to “biomap” microbial communities across the globe, an effort known as the Earth Microbiome Project). The work so far is already sparking some key questions in the digital health realm. Can our bacterial body guests, for example, play a role, in precision medicine? Well, funny you should ask.