A prevailing theory in the tech industry is that smartphones will one day be replaced by normal-looking glasses that display virtual information onto the real world.

Leaders like Facebook CEO Mark Zuckerberg believe the nascent technology, known as augmented reality, could eventually replace all screens, including TVs. They say that when you can display virtually anything onto the world around you, the need for physical displays is essentially erased.

The problem is that, while a traditional computer has a mouse and a smartphone has a touchscreen, there's no input equivalent for AR yet. How do you dismiss a notification or respond to a text when you're wearing a computer on your face?

The answer lies in connecting directly with your brain, Facebook chief technology officer Mike Schroepfer recently told Business Insider. And it's a big part of why Facebook is working on a brain sensor capable of letting people type using only their minds.

"It has huge applications for communication and connection," Schroepfer said of Facebook's recently announced brain-computer-interface (BCI) sensor, which the company is aiming to have a working prototype of in 18 months. "And it’s also I think a critical technology for AR and VR in the long run. Because the problems of input are a big challenge there."

While Facebook believes that the first truly AR glasses won't arrive for 10 to 20 more years, early versions will have some way of connecting to the human brain, according to Schroepfer.

"I think what you’ll see is nascent versions of BCI being integrated into early AR systems," he explained. "If you are just able to move your eyes and do a single click from your brain... I’ve now just rebuilt the mouse."