While the smartphone rules today's tech world as the primary computing device, the next big hardware platform is widely expected to be some version of augmented reality glasses.

The big picture: Facebook, Apple, Microsoft and Google are all pursuing this vision, and many pieces are starting to fall into place. But the holy grail of an affordable computer inside something not much bulkier than a standard pair of glasses is likely still a few years off.

How it works: Such glasses allow users to see what's in front of them, but with digital information overlaid, such as map directions, contact information and messages. Cameras and microphones capture input like video and sound, with speech likely to play a key role.

Who is involved: Apple, Google, Facebook and Microsoft have all shown an interest and invested heavily in the underlying technologies. Analysts also expect phone makers like Samsung, and PC makers like Lenovo, to get in on the act.

Be smart: If you look closely, you can see some of the key underlying technologies already being developed and tested in plain sight.

• Facebook plans to debut smart glasses this year, in a more advanced twist on Snap’s spectacles that Facebook likely hopes will be consumers' stepping stone to far more sophisticated future products. The company's Oculus unit, meanwhile, focuses mostly on virtual, not augmented, reality, but the Oculus Quest 2 and other VR headsets can also deliver AR using cameras.
• Microsoft already sells Hololens, which packs the power of a Windows 10 computer into a headset, albeit one that is still too bulky and expensive to appeal to consumers. Microsoft has made it available to developers and some enterprise customers, and is also doing early work with the U.S. Army.
• Google Glass, the first device in this category that attracted mainstream attention, flopped as a consumer product, but a slightly updated version is still being sold to businesses.
• Apple been quietly making lots of moves, including reportedly putting executive Dan Riccio in charge of VR/AR efforts. Bloomberg and The Information report Apple is readying a VR headset to hit the market as soon as next year. The device could also use cameras to see into the real world, paving the way for the eventual release of true AR glasses.

The intrigue: Both Apple's AirPods and Apple Watch represent efforts toward miniaturizing technology and testing individual components, such as the spatial audio feature included with the latest AirPods Pro, that could be crucial to making advanced AR glasses work.

• Several companies hope to solve some of AR glasses' tough technical challenges by splitting the computing work among multiple devices. Qualcomm, among others, aims to offload some of the glasses' processing needs onto users' smartphones.

Yes, but: The technical hurdles are many, especially if the goal is really something as light and inconspicuous as eyeglasses. They include:

• Miniaturization of components like cameras, microphones and processors, which are tinier than ever but still add up to clunky frames when taken together.
• Battery life that lasts more than a couple hours between charges.
• Heat, which chips still give off when they're working hard — annoying for a phone but a real problem for a device that rests on your face.
• Display, with most AR glasses today having tunnel vision in terms of where imagery can be projected, as well as struggling to work well in bright sunlight.
• Cost, as all the tech adds up to a product that costs several thousand dollars.

Bringing AR glasses to market will be a big technical challenge, but societal questions could prove even more treacherous in rolling out a product that amounts to a nearly invisible computer that is always recording.

Why it matters: Computer components will inevitably get small, cheap and light enough to make the smart glasses of the future a reality. But, according to some of the key players in the emerging field, it will take concerted effort to address privacy implications and related concerns.

Driving the news: That's part of why Facebook has launched Project Aria, an effort to measure the societal reaction to smart glasses.

"How do you fit this all into a socially acceptable, comfortable form factor that people feel fits the way they want to express themselves? And then of course you have to consider the people who don’t have the glasses. How does this impact them, how do you solve for their discomfort? How do you bridge the privacy concerns with always-on cameras and microphones?"

Our thought bubble: Even if users can be persuaded to trust that their glasses aren't spying on their friends and families or recording their private conversations, the new devices will demand new norms for every conceivable social situation.

• Companies rolling out glasses will have to pray that those norms emerge and evolve fast and head off the kind of dramatic failures — embarrassing or appalling incidents that go viral — which might doom the products.

Flashback: These questions have always accompanied this technology. They came up back when Google first introduced Project Glass back in 2012.

• Part of what doomed the pioneering smart glasses as a consumer wearable — beyond the immature technology — was that they were widely viewed as creepy and intrusive. (Remember this?)

When I asked Salesforce CEO Marc Benioff in an "Axios on HBO" interview last year whether he regretted investing so much in offices, especially in high-rise buildings, he told me to ask again in a year.

The latest: It's been nine months, but already Salesforce is envisioning a much more partial, limited return to the office for its workforce. The company announced Tuesday a new "work from anywhere" strategy that gives employees far more flexibility to choose what place they consider the office.

Driving the news: Salesforce said most employees will work from the office only one to three days a week, while some will work fully remotely. It now foresees that only the smallest share of its workforce will come to an office each day.

• That will also mean using its physical space differently. "Gone are the days of a sea of desks — we'll create more collaboration and breakout spaces to foster the human connection that can't be replicated remotely," Salesforce said in a blog post announcing the changes.

Between the lines: It's a major shift for Salesforce, which has always gone big pursuing its goal of bringing people together, both with its preference for skyscraper offices and its massive Dreamforce conferences, which have historically taken over a huge swath of downtown San Francisco.

The big picture: Companies across the technology field similarly foresee a more flexible approach to work, where many workers come into the office only on certain days and some work entirely remotely.

Sentropy, a startup backed by Reddit co-founder Alex Ohanian, has spent much of its first year focused on helping protect digital platforms from abuse using machine learning. On Tuesday, it announced a new service aimed at helping Twitter users avoid abusive comments.

Why it matters: Individuals, especially prominent women, people of color and LGBTQ people, encounter frequent online abuse and often have to first view inflammatory posts before they can take action, such as blocking or muting those doing the harassment.

• "Today if you go on Twitter and are being harassed or dealing with hate speech, you have to see it to process it," says Sentropy VP of product Dev Bala. "The opportunity we are providing here is to programmatically deal with that and essentially pre-moderate the feed."

Details: Sentropy's new Protect service, now in beta, lets individuals choose to let Sentropy automatically take action on tweets or, if they prefer, simply flag potentially offensive content and let the individual decide what actions to take.

The big picture: Sentropy CEO John Redgrave said that because Twitter already has tools and APIs for blocking and muting users, the platform was a natural place to start. But, he said, "The vision is not Twitter-specific. This is much bigger."

On Tap

• Uber is slated to report earnings after the markets close.

Trading Places

• Contentful, a content platform for digital-first businesses that’s part of a new program to diversify corporate boards, said Tuesday it is adding Scalyr CEO Christine Heckart to its board.

ICYMI

• Twitter shares rose after the company delivered better-than-expected quarterly sales and earnings, though user growth for the most recent period fell slightly short of estimates. (Axios)
• Match Group said it will pay $1.7 billion to buy Hyperconnect, a Korea-based social discovery platform. (Axios)
• My former Recode colleague Johana Bhuiyan takes a look at the scary power of facial surveillance when used to detect race on a population. (LA Times)
• Democrats plan $7.6 billion for remote learning in COVID package. (Axios)

I'm sure some of you saw this yesterday, but for those who didn't, this video of a lawyer showing up to court on Zoom with a cat filter is amazing.

• For those that have seen that (and those who haven't) I give you this video of actual feline exploration. Be sure to watch until the end.