This book is an in-depth exploration of blockchain and smart contracts technologies, systematically addressing their theoretical foundations while highlighting concrete applications in several key sectors. It begins by defining the fundamentals of blockchain and smart contracts, then ventures into the legal domain, analyzing the implications of automated contracts from both backend and frontend perspectives. A particular focus is placed on a sustainable design for cryptocurrencies, anticipating the principles and expectations of the future. The book then provides a detailed taxonomy of blockchain's financial applications, while also examining its role in managing scientific workflows. The fascinating world of NFTs is also explored, from the tokenization of fine arts to innovative event ticketing systems. The convergence between ontologies and blockchain technology is then highlighted, followed by an in-depth assessment of the implications of this technology in the telecommunicationssector, including a SWOT analysis of next-generation cellular networks. Written by academic researchers and industry experts, this book offers a complete and nuanced perspective on the transformational potential of blockchain.