Facebook has announced the acquisition of mobile messenger WhatsApp for $16 billion. The deal includes $4 billion in cash, $12 billion in Facebook shares and an additional $3 billion in vesting restricted stock units for the WhatsApp team over the next four years.

At the time of acquisition, WhatsApp had picked up an impressive 450 million active monthly users and was growing by 1 million new registered accounts per day. That’s up from 400 million monthly users last December.

While the deal represents a much-deserved payout for the WhatsApp team, it’s also likely to come as a disappointment to users that had chosen WhatsApp as an alternative to Facebook’s own Messenger product. Similar to the terms of Instagram’s deal, WhatsApp will remain as an independent brand and team. That means that WhatsApp and Messenger will have the awkward situation of being both competitors and siblings in the marketplace.

In a blog post, WhatsApp CEO Jan Koum reassured users that the acquisition won’t result in any changes for them. Koum will join Facebook’s board of directors.

In 2011, Facebook acquired mobile messaging service Beluga. It kept it open for a few months, before folding it into Messenger and shutting it down.

Mobile messaging apps have been hot this past year, and larger tech companies are finally getting around to snatching them up. Japanese ecommerce giant Rakuten bought Viber last week for $900 million.

See also: WhatsApp is leading the mobile messaging battle, but will it win the war?