In 1609 Galileo Galilei turned his gaze, magnified twentyfold by lenses of Dutch design, toward the heavens, touching off a revolution in human thought. A decade later those same lenses delivered the possibility of a second revolution, when Galileo discovered that by inverting their order he could magnify the very small. For the first time in human history, it lay in our power to see the building blocks of bodies, the causes of diseases, and the mechanism of reproduction. Yet according to Paul Falkowski’s Life’s Engines:

Galileo did not seem to have much interest in what he saw with his inverted telescope. He appears to have made little attempt to understand, let alone interpret, the smallest objects he could observe.

Bewitched by the moons of Saturn and their challenge to the heliocentric model of the universe, Galileo ignored the possibility that the magnified fleas he drew might have anything to do with the plague then ravaging Italy. And so for three centuries more, one of the cruellest of human afflictions would rage on, misunderstood and thus unpreventable, taking the lives of countless millions.

Perhaps it’s fundamentally human both to be awed by the things we look up to and to pass over those we look down on. If so, it’s a tendency that has repeatedly frustrated human progress. Half a century after Galileo looked into his “inverted telescope,” the pioneers of microscopy Antonie van Leeuwenhoek and Robert Hooke revealed that a Lilliputian universe existed all around and even inside us. But neither of them had students, and their researches ended in another false dawn for microscopy. It was not until the middle of the nineteenth century, when German manufacturers began producing superior instruments, that the discovery of the very small began to alter science in fundamental ways.

Today, driven by ongoing technological innovations, the exploration of the “nanoverse,” as the realm of the minuscule is often termed, continues to gather pace. One of the field’s greatest pioneers is Paul Falkowski, a biological oceanographer who has spent much of his scientific career working at the intersection of physics, chemistry, and biology. His book Life’s Engines: How Microbes Made Earth Habitable focuses on one of the most astonishing discoveries of the twentieth century—that our cells are comprised of a series of highly sophisticated “little engines” or nanomachines that carry out life’s vital functions. It is a work full of surprises, arguing for example that all of life’s most important innovations were in existence by around 3.5 billion years ago—less than a billion years after Earth formed, and a period at which our planet was largely…