Today Nike unveils the Zoom Vaporfly Elite, a concept running shoe that three world-class runners will wear this spring during the Breaking2 initiative to run a sub-two-hour race. Given the trajectory of human athletic performance—in 1906, the best marathoners clocked in at just under three hours—a sub-two-hour run seems achievable, if not inevitable. But scientists, athletes, and designers agree this is a mighty goal. "It's ones of those big barriers of human potential," says Tony Bignell, VP of footwear innovation at Nike. The Vaporfly Elite is the sportswear giant's vehicle for crossing that threshold and perhaps even upstaging the Adidas Adizero Sub2, the new marathon shoe from its chief rival.

Nike began this endeavor in earnest in 2014, although its designers say they started dreaming about such a shoe more than a decade ago. A confluence of factors make now the time to go for it: Bignell says advances in 3-D knitting and cushioning technology, and athletes already close to breaking the two-hour barrier, help.