Foldable smartphones are expensive and fashionable right now, but the devices use plastic, not glass, to achieve their folding form. Samsung debuted its Galaxy Fold smartphone last month, while Huawei showed off its folding Mate X. Both phones come at a premium price tag, but have set expectations for what future folding smartphones could look like.

“Corning is currently working on developing an ultra-thin, durable and optically advantaged glass solution for the inside cover of a continuous display that can bend at a tight radius hundreds of thousands of times without significant damage at the fold,” a Corning spokesperson told Fortune in an email. “We are working with our customers on this challenge and are currently sampling our development glass with them to optimize the product for their design requirements.”

John Bayne, general manager of Corning, told Wired the biggest challenge scientists working on the project must address is creating a glass that is thin enough to bend, while also ensuring the display is resilient enough to withstand the folding and unfolding actions.

Despite a leaked folding smartphone patent, Apple has not commented on whether it has ambitions for a folding iPhone. However, a folding glass breakthrough from Corning offers the tantalizing prospect of a future folding iPhone, complete with a glass display.

Apple showed its faith in Corning in 2017 when it announced a $200 million investment to “support Corning’s R&D, capital equipment needs and state-of-the-art glass processing.”