NFTs are a real buzz at the moment. They let us tokenise things like art, collectibles, even real estate. NFTs started in 2017 with CryptoKitties (a game to breed and trade digital kittens) and CryptoPunks and gradually increased over the last years, but it exploded in 2021 (i.e. in 2020 the market was estimated to $250 million over the whole year, while in the month of February 2021 alone already $360 million of NFTs were traded). These enormous prices definitely attract a lot of media attention and investors, but nonetheless NFTs remain difficult to grasp. While for traditional art, the owner has the physical artwork in his possession, this is not the case at all for NFTs. For example, the NFT for the Beeple picture sold for the record amount $69.3 million can perfectly be downloaded on the internet at no cost. This downloaded file will be identical to the digital file owned by the buyer (i.e. the copy is literally as good as the original).