How to prevent the Facebook app from automatically playing videos (Android and iPhone)

Facebook recently introduced the video auto-play feature - with it, instead of requiring you to tap the play button, videos automatically start playing as you stumble upon them in your feed. For many Facebook users out there, it's surely a very useful and intelligent feature, but we can imagine that there is also a good number of users who just can't develop a liking for their videos to be auto-played, and would be grateful if there's a way to revert things back to how they were.