Twitter boss Jack Dorsey sold his first tweet as an NFT for just over $2.9 million dollars on Monday. The tweet is in the form of a non-fungible token (NFT) - a kind of unique digital asset that has exploded in popularity so far in 2021. Each NFT has its own blockchain-based digital signature, which serves as a public ledger, allowing anyone to verify the asset's authenticity and ownership. The tweet - "just setting up my twttr" - was Dorsey's first tweet, made on March 21, 2006. The buyer, Sina Estavi, is CEO of the blockchain company Bridge Oracle based in Malaysia.