For about a decade, Meta has been working on an audacious project: AR glasses stylish enough to pass as regular eyewear, and yet so powerful that they could one day replace the smartphone. “When we started, we actually thought that there was less than a 10 percent chance that we could make it happen,” admits Meta AR devices VP Ming Hua.

And yet, at this week’s Meta developer conference, the company showed off Orion: An AR glasses prototype that comes closer to this vision than any other device in its category, leading Meta CEO Mark Zuckerberg to call them “the most advanced glasses in the world.”

Meta has spent tens of billions of dollars on its AR hardware plans, and the company is not alone in its pursuit of wearable computing. Google, Apple, Samsung, and others all are working on AR glasses. Snapchat maker Snap unveiled its latest version of its AR Spectacles glasses at an event last week.

Snap’s Spectacles, and Meta’s Orion glasses, do offer a fascinating look at the future of personal computing—a future that now appears just years away. However, they also show why it’s been so challenging for tech companies to make AR glasses, and why none of the big companies are ready to turn their prototypes into mass-market products just yet.

Or as Zuckerberg put it this week: “The technical challenges to make them are insane.”

Hands-on with Meta’s Orion glasses

At first glance, Meta’s Orion glasses do look more or less like a regular pair of glasses, albeit somewhat oversize, with thick rims and temples. Once you put them on, you can see holograms overlaid over your view of the real world. These include a number of different apps, including Instagram, Facebook Messenger for chats and video calls, a web browser, videos, a retro space shooter, and a 3D game of Pong you can play against another person wearing the same set of glasses.

More impressive than the apps themselves is the fact that Orion can display up to three of them next to each other without forcing you to turn your head. That is because Orion’s optics feature a 70-degree field-of-view, which is significantly wider than that of any other pair of augmented reality glasses currently in the market. Snap’s new AR Spectacles, for instance, only have a 47-degree field of view, which forces users to frequently turn their heads when they look at AR objects.

“The field of view is transformational,” agrees Moor Insights & Strategy analyst Anshel Sag. “It addresses one of the biggest problems in AR.”

Meta’s Orion glasses use eye tracking to help users navigate through menus, and come with a futuristic wrist-worn controller that looks a bit like a fitness tracker. The wristband measures electrical currents to identify nerve signals traveling to and from the brain, which makes it possible to track subtle finger movements that can then be used to navigate through Orion’s on-screen menus.

“This lets you do very small micro gestures,” explains Meta’s senior product management director Rahul Prasad. “You don’t have to hold your hand up in the field of view of the glasses, you can keep your hand down by your side.”

Meta also integrated hand tracking into the glasses, added an outward-facing camera to let AI recognize real-world objects, silicon carbide lenses for optimized optics, as well as custom-designed chips to minimize power consumption and achieve up to three hours of battery life.

All of this makes for a very impressive piece of technology, agrees Sag, who has tried dozens of different AR and VR devices over the years. “I haven’t seen a pair of glasses that have this much capability,” he says. “It is the most advanced in almost every way.”

AR glasses are here—but you can’t buy them yet

However, integrating all of that advanced technology also comes with a significant downside. At this point, Orion would be much too expensive, and too hard to manufacture, to achieve mass-market scale. The company only produced a small number of Orion glasses that will primarily be given out to company executives and employees. “We’re going to be deploying it internally,” Prasad says. “It becomes our time machine to learn what the future looks like.”

Snap isn’t quite ready to sell its AR glasses to the public either yet; Spectacles are even bulkier than Meta’s Orion glasses, and their internal battery lasts just 45 minutes per charge. Spectacles do have brighter and sharper AR overlays than Meta’s Orion glasses, but their small field-of-view significantly reduces the sense of immersion.

That’s why Snap is treating its AR glasses as a developer kit, and only making it available to AR developers willing to pay $99 per month for access to to the hardware via a subscription plan that comes with a one-year minimum commitment.

Meta, meanwhile, has plans to sell the next version of Orion to consumers. The company is already trialing a higher-resolution version of the glasses, and also plans to make the glasses, which currently weigh about 100 grams, lighter and less bulky. But the biggest goal is a more affordable price. “We want to get the cost down significantly,” says Prasad, suggesting that the device could cost about as much as a smart phone in the future.

When that future will arrive is still unclear. This month’s hardware introductions show that the industry still has a lot of work to do—but they also prove that AR wearables are within reach, with Sag projecting that we could see consumer-grade AR glasses within the next three years.

“When you look at the chipsets, optics and display technologies, things are moving along much faster than they were two or three years ago,” Sag says.