Few revolutions in science have been more far-reaching - but less understood - than the quantum revolution in physics. Everyday experience cannot prepare us for the strange phenomena of the subatomic world, where quantum effects become all important. Here, particles can look like waves, and vice versa; electrons seem to lose their identity and instead take on a shifting, unpredictable appearance that depends on how they are being observed; and a single photon may sometimes behave as if it could be in two places at once. In the world of quantum mechanics, uncertainty and ambiguity become not just unavoidable, but essential ingredients of science. But then comes an even more disturbing thought: When we look at the world around us, why do we not see the quantum weirdness that pervades its most fundamental structure? If the familiar world of everyday experience is built from ambiguous and unreliable subatomic ingredients, how can it be as solid, dependable, and predictable as we know it to be? David Lindley explains how physicists are finally beginning to find an answer to the most perplexing question of all: How does our Newtonian world arise from its quantum foundations? With that understanding, Lindley brings the quantum revolution full circle, showing how the familiar and trustworthy reality of the world around us is actually a consequence of the ineffable uncertainty of the subatomic quantum world - the world we can't see.