Every president since Ronald Reagan has left a note for his successor, and President Biden is the first to write a letter to someone who is both his successor and the predecessor who left a note for him.

This will mark the first time that a president who has received a letter from an outgoing president may well be writing a letter to the same person who's the incoming president'

Biden won't enforce the TikTok ban set for Sunday, January 19, his last day in office. It will be up to the Trump administration to enforce the law.

The Biden administration doesn't plan to take action that forces TikTok to immediately go dark for U.S. users on Sunday, an administration official told ABC News.