(CNN) Donald Trump and Pope Francis are not the first president and pontiff to tweet. But they are the first to use the social media platform so prolifically, and pointedly.

All eyes will be watching those accounts in the hours after Trump and Francis meet in Vatican City on Wednesday. (Here's an in-depth preview of their historic encounter , which will bring together two complex and contrasting personalities.)

The Pope and President are expected to put aside their differences during the meeting, but, as their Twitter history shows, they haven't always been singing the same tune.

One big caveat: The Pope doesn't tweet himself; his staffers often choose snippets from his sermons and speeches. So, we should probably resist the urge to read his tweets as 140-character assassinations of Trump, or anyone else.