When HoloLens officially launched in 2016, it was a 1.3-pound head-mounted display with depth-sensing cameras and an optical projection system that beamed holographic images directly into your eyes. While wearing one, you might see anything from a floating web browser to a cartoon fish in a bathtub to a three-dimensional motorcycle—all while still seeing the real world around you. Or you might see a remote technician pop up in your eye frame and show you how to fix a light switch. It isn’t a consumer device now, and it certainly wasn’t then, but Microsoft was trying to show off a wide variety of applications that could be easily grasped by regular people.

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The HoloLens was available only to developers when it first launched, since Microsoft wanted to spur development of new apps. (No AR or VR headset is worth the money without compelling apps; that was true then and is still true now.) Later that year, a version of HoloLens started shipping to any consumer in the US or Canada who had $3,000 to spend.

The first HoloLens wasn’t a “success” in the way that you might describe the success of other technology products, whether that’s based on sales, ecosystem lock-in, or pure cachet. In some ways, it wasn’t meant to be a blockbuster hit in a public-facing way. But it was the first mixed-reality wearable that ran on a holographic-specific operating system—and it wasn’t a pair of lightweight smart glasses. It was an untethered headset running Windows 10, which meant it was an actual working face computer.

Still, early customers had their complaints: It was heavy, it was unwieldy, it didn’t feel immersive enough. And Microsoft heard them, loud and clear.

Put Your Heads Together

One of the most obvious updates to HoloLens 2 is its build. The first HoloLens was front-heavy, a whole bunch of components loaded onto your forehead. For this new version, Microsoft split up the pieces, positioning the lenses and some computing power in the front and moving the rest of it to the back.

Microsoft’s senior director of design, Carl Ledbetter, calls this a split-architecture design. It came loaded with its own engineering challenges, because cables had to run between the front and back parts of the headset. These are now built into the arms of HoloLens 2. Ledbetter says this new form factor was critical to achieving a certain level of comfort and balance on the new model. “With HoloLens version one, there were just a lot of things we didn’t know we didn’t know,” Ledbetter says as he leads me around Microsoft’s Human Factors lab. “But luckily, since it’s been out there for three years, we’ve been able to talk to a lot of customers.”

The Human Factors lab is a cavernous space filled with as many mannequin heads as human ones; the latter are bent over their desks, toiling on the latest designs. There are also ear molds, gesture-control wristbands, custom-made eye depth gauges. For the past three and a half years, Lebetter and his team have used these tools to design a new HoloLens headset that would fit well on 95 percent of heads, regardless of gender, ethnicity, or age. It’s not just about finding the right fit, Ledbetter says, but about having empathy for the wearer. At one point, he hands me an intentionally oversized Xbox gaming controller. “There,” he says. “You’re five years old.”

Ledbetter and his team have scanned over 600 human heads in the Human Factors lab. A hundred other people have been put through “stress tests” with HoloLens 2 prototypes—asked to watch a long movie or play the tabletop game Jenga or converse with other humans. The goal was to have people forget they were wearing it, ideally for up to two hours. In some cases, “we were getting more than two hours, and people weren’t taking it off at all,” Ledbetter says. Some tests involved sensors, attached to subjects’ necks, that measured muscle load or fatigue. Ledbetter claims, based on this data, that the new HoloLens is three times as comfortable as the old one.