Mark Zuckerberg is highly adept at addressing Facebook’s greatest threats.

He spent $1 billion on Instagram because that’s where young people were posting photos. After getting rebuffed by Snapchat, he shelled out a whopping $19 billion for WhatsApp to make sure Facebook had a leading messaging platform. And to address Facebook’s weakness in consumer devices, he plopped down $2 billion for Oculus.

Now there’s blockchain, a technology that, by its very nature, poses a future threat to Facebook.

Blockchain is a distributed ledger with data stored across a network of computers and rules that are enforced by its many participants. It’s the opposite of Facebook, which is a massive centralized organization that controls all the infrastructure underlying the 2 billion global users on its proprietary social network.

Imagine a vast online network in the future where we all hang out, chat and buy things, but that’s not owned by Facebook or Google or Amazon. That’s the promise some people see in blockchain.

“I certainly don’t think blockchain is an existential threat to Facebook today,” said Spencer Bogart, a partner at Blockchain Capital, a San Francisco-based venture firm that invests in blockchain companies and cryptocurrencies. “Could it be? Yes, longer term. That’s why they want to be smart and stay engaged.”

On Tuesday, Facebook offered its most significant acknowledgment to date that blockchain is real and not just an overfunded science experiment bolstered by the hype around bitcoin.

David Marcus, one of the company’s top executives, the head of its Messenger platform and a former CEO of PayPal, said that he’s leaving Messenger and “setting up a small group to explore how to best leverage blockchain across Facebook, starting from scratch.” Marcus is also a board member at cryptocurrency exchange Coinbase.

It’s a vague start for Facebook. But it’s notable because of Marcus’s high profile and because the announcement comes four months after Zuckerberg said in his 2018 mission statement that he was interested in studying the “positive and negative aspects” of the decentralized nature of technologies like cryptocurrencies.

Recode reported that Marcus will be joined by Instagram executives James Everingham and Kevin Weil, who helped Facebook fend off the threat from Snap with a series of rapid-fire updates to Instagram that mimicked key Snapchat features.

Zuckerberg isn’t pulling a WhatsApp or Oculus — at least not yet — and making a multibillion-dollar acquisition to address a competitive threat. He’s giving Marcus the tools to see how blockchain can be used internally and to make sure the company is closely monitoring the broader ecosystem and where Facebook may be most vulnerable.

Bogart said Facebook is probably paying close attention to Robinhood, an investing app that targets young audiences and recently launched a crypto trading platform. The Wall Street Journal reported in March that Robinhood’s surging popularity among millennials has attracted venture investors, who are poised to value the company at $5.6 billion.

“Apps like Robinhood are occupying a larger percentage of Facebook’s most valuable demographic,” Bogart said. “Just that screen time — people spending time there instead of Facebook — is a threat to them.”

Blockchain enthusiasts see an opening to take Facebook out of the equation. Messaging app Telegram, which has grown to 200 million users without advertising or any other business model, has raised close to $2 billion from private investors to build a blockchain-based network. And last month, angel investor Jason Calacanis started the Open Book Challenge, in which seven companies will each receive $100,000 in investment money to start building a Facebook replacement.

“Facebook is actively trying to shut down the open web,” Calacanis wrote in a blog post about the competition. “That’s an opportunity for clever founders to double down on solutions that Facebook and Google do not control.”

None of these efforts are foreign to Zuckerberg. He has a knack for understanding what’s popular, what’s trending and what works. He also has a board that includes venture capitalists Marc Andreessen and Peter Thiel, who have been active investors in crypto and blockchain. Zuckerberg is unlikely to be blindsided.

Whether blockchain technology can exist inside Facebook is an open question. A digital payment system for Messenger and WhatsApp would be an obvious place to start and would certainly make sense as a way for users to send money and buy goods.

But it’s easier said than done. Blockchain technology has yet to prove that it can serve tens of millions or hundreds of millions — not to mention billions — of users. Think back to December, when a novel game called CryptoKitties suddenly took off and occupied so much compute power that it clogged up the ethereum network and knocked down other projects.

“The technology is still pretty nascent,” said Bogart. “There are scalability challenges.”