From the first spark of fire to the frontiers of energy, medicine, and space, a pioneering account of the invisible force that connects it all. Friction, the force that resists motion, is synonymous with difficulty and complication. If you've ever replaced tires worn smooth by the road or reached for a can of WD-40 to fix a creaking door hinge, then you know the headache this force can cause. In this book, Jennifer Vail reveals beneath the difficulty and complication a force as enigmatic and intriguing as it is central to the human story. She traces how, from the moment we first harnessed the power of fire to the Industrial Revolution and beyond, the quest to manipulate friction has driven innovation, culture, and even our own evolution. Today, as scientists study friction in the most unexpected of places, they're learning why some viruses lie dormant for years while others devastate our cells immediately; where elusive dark matter might be found; and how the climate crisis ought finally be addressed. And yet, for all they've learned, scientists still haven't cracked the greatest mystery of all: how to bridge the distinct laws that govern friction at its largest and smallest scales. Connecting the discoveries of historical luminaries like Newton, da Vinci, and the Wright brothers to the latest breakthroughs in engineering, Friction is a captivating biography of this unsung hero of the physical world.