http://www.newsweek.com/facebook-messenger-dark-mode-how-activate-get-turn-1350155

Facebook has been quietly rolling out a feature that will let users of its Messenger app communicate in "Dark Mode," a setting that switches the current white-screened interface to a night-friendly black theme. 

The no-frills unveiling of the display is part of the company's efforts to streamline its private messaging app, which has developed (or, arguably, devolved) to include gaming, business and payment tabs. To activate the hidden feature, users must first send the left-facing crescent moon emoji to someone in their chat list. (If sending out random emojis to contacts sounds unappealing, users can also send the moon to themselves.) A slew of tech outlets and blogs reported on the added feature Saturday, including Fast Company, Digital Hacks and The Verge. Newsweek confirmed the addition of "dark mode" to Messenger on several devices.