The Nike EXP-X14 running shoes pushes the boundaries of lifestyle footwear through the use of numbers and transparent design elements. Here's what you need to know about it. EXP is shorthand for "experiment," which was essentially how the Nike Sportswear designers adapted performance running features into a lifestyle shoe. Second part of the shoe's name, X14, was the original internal codename for Nike React technology (which is used in the shoe's midsole to provide cushion for all-day comfort). N3546, which is printed on the medial side, represents Steve Prefontaine's fastest mile (3 minutes and 54.6 seconds) and nods to Nike's rich history in running. Its look with its translucent upper, this shoe is a modern take on the Nike Zoom Drive (a late-90s running shoe).