Facebook announced Tuesday it is adding the option to send other users money via its Messenger app.

Messenger is the social network’s separate, but required, app for chat — basically an updated version of AOL Instant Messenger, for those of you still using Internet Explorer.

Marketplace’s Tracey Samuelson tells us how the move could bring mobile payment into the mainstream, and open up new revenue opportunities for the site. The announcement language suggests users will only be able to transfer money to people who are already their Facebook friends, but Facebook could expand the service in the future, possibly creating more opportunity for businesses.

Facebook reports the money feature will roll out during the next few months in the U.S. To send money, users start a message with a friend, tap the “$” icon and enter the amount they want to send, and then tap “Pay” to send money. The funds are transferred right away, but the first time someone sends of receives money in Messenger, a Visa or MasterCard debit card has to be attached to their account.

A pin, or Touch ID on iOS devices, will add another layer of security, so hopefully toddlers on tablets everywhere don’t end up sending strangers cash.