You can see an example of a tweet turned into an nft here.
They had previously been on the ethereum blockchain. They have moved to a 2nd layer eth meaning ethereum chain called by some matic if they have been around a while and its now called polygon after a name change sometime ago.
The collection is called Tweets and its is a verified collection on opensea. You may have heard of the Twitter founder selling his 1st tweet for a large amount last year this is the platform he used.
You can mint them by signing into your Twitter account on their site and hitting the mint button, then verify it in your crypto wallet like a metamask wallet.
You can find more info about them here
You can find my 2nd Twitter account talking about nft and coins, stocks and more at https://twitter.com/cavstheblockfan