Since the birth of Bitcoin, in early 2009, an explosion of researches and investments were unleashed towards a new disruptive technology called blockchain. This new technology, that consists in a sequence of blocks cryptographically linked one to each other, provides a fully auditable and immutable ledger, where data, once stored, cannot be modified. The blockchain aims to revolutionize the interaction between people and machines in an untrusted distributed environment without the need of a central trusted authority. From the birth of Bitcoin, most applications built on top of such technology were mainly in the FinTech sector, regarding exchange of cryptocurrencies, in the so-called permissionless blockchain network.