Facebook’s latest experiment involves adding Face ID / Touch ID protection to Messenger chats.
When enabled, users will need to authenticate their identity using Face ID, Touch ID, or their passcode before they can view their inbox, even if their phone is already unlocked. […] The company is currently testing the new security feature among a small percentage of Messenger’s iOS users, though it could eventually be available more widely, including on Android.
I’d love to seen an option to lock any app with Face ID / Touch ID.
Check It Out: Facebook Considers Adding Face ID to Messenger Chats