The social media site, Twitter, has for the first time ever, fact-checked a tweet by Donald Trump.
The tweet-in-question was posted yesterday - in it, the President falsely accused the governor of California of sending mail-in ballots to undocumented immigrants.
In response to the posts, the social networking site posted a small blue exclamation mark below the tweet, and had a link, which said the claims were unsubstantiated.
Well, in response to that move, Trump threatened to either heavily regulate, or even shut down the social networking site.
In follow-up tweets, he accused the giant of interfering with the 2020 Presidential Election, and that they were stifling free speech.
Washington correspondent Simon Marks speaks to Susie Ferguson.