Facebook introduced a dark theme for its Messenger application.
What is known
Night mode for a month
A number of other applications, including YouTube andTwitter also offers a dark mode. It can help extend the battery life of phones, especially those with OLED screens. Meanwhile, if rumors are to be believed, the next major versions of Android and iOS should include system-wide dark mode settings.
Recall that Facebook Messenger can return back to the main application. Perhaps the new mode will be available there.