Facebook plans to integrate its messaging services on Instagram, WhatsApp and Facebook Messenger.
While all three will remain stand-alone apps, at a much deeper level they will be linked so messages can travel between the different services.
Facebook told the BBC it was at the start of a "long process".
The plan was first reported in the New York Times and is believed to be a personal project of Facebook founder Mark Zuckerberg.
Once complete, the merger would mean that a Facebook user could communicate directly with someone who only has a WhatsApp account. This is currently impossible as the applications have no common core.
The work to merge the three elements has already begun, reported the NYT, and is expected to be completed by the end of 2019 or early next year.
What is Facebook's plan?
Facebook probably didn't want to talk about this in the middle of a privacy scandal, but its hand was forced by insiders talking to the New York Times.
Until now, WhatsApp, Instagram and Messenger have been run as separate and competing products.
Integrating the messaging parts might simplify Facebook's work. It wouldn't need to develop competing versions of new features, such as Stories, which all three apps have added with inconsistent results.
Cross-platform messaging may also lead the way for businesses on one platform to message potential customers on another.
And it might make it easier for Facebook to share data across the three platforms, to help its targeted advertising efforts.
But bigger still: it makes Facebook's suite of apps a much tighter, interwoven collection of services. That could make the key parts of Facebook's empire more difficult to break up and spin off, if governments and regulators decide that is necessary.