Sneakers are quickly growing into a $90 billion business–but they’re all built the same way, more or less, constructed out of a combination of soles and uppers. Nike has React and Flyknit. Adidas has Ultraboost and Primeknit. What if we could replace just part of a shoe, rather than the whole thing? It could be greener, cheaper, and more customizable, too. That’s the premise of a new project from University of Eindhoven student Lucille Nguyen, who developed a series of working prototypes called “Up-Part” shoes. “[We] would sell the sole and the upper separately. Either can be replaced when damaged, hence limiting waste,” says Nguyen. “Since every parts can be detached by the user, it is also easier to recycle.” The shoes wouldn’t be sold as shoes, but as kits designed to be crafted together. You start with the sole. On top, you add the upper itself, complete with tongue, secured through lacing or straps (depending on whether it’s a Converse-esque tennis shoe or something more akin to a Birkenstock sandal). Read more at Fast Company.