Blockchain technology and the invention of smart-contracts running on it have given rise to Decentralized Finance. At the time of its birth, DeFi was seen as a response to the 2008 crisis and a hope to democratize finance. By eliminating the role of intermediaries and fluidifying property through tokenization, finance would become accessible to all. To overcome all the obstacles it faced (volatility, security issues, distrust etc.), DeFi had to find original ways to develop, by leveraging sociologically diverse communities of enthusiastic developers, users and investors from all over the world. In particular, it has distinguished itself in the fields of communication, marketing and community building through an original use of social networks and messaging tools. We have specifically emphasized these latter aspects, based on our professional experience and interviews with experts working in the field. It appears that DeFi is potentially interesting for companies. Indeed, Blockchain technology is generalizable to many other areas of economic activity beyond finance. Moreover, the DeFi communities foreshadow the communities of entrepreneurs and users/consumers of the future Web3.0. DeFi is the manifestation of a new era of the Internet. Due to key elements of blockchain and smart contracts, the value of data could be wrested from the hands of Internet giants, that control the ad market, and be restituted to businesses and consumers. Through the direct relationship with the consumer, this technology is becoming a powerful tool for optimizing business operations, reducing costs and creating value. Businesses will have to reconsider relationship with their customers, in a spirit of community and direct interaction with them (which blockchain allows, i.e. through remuneration of the user/customer). However, if blockchain technology is mature, its use is still too amateurish. In this context, it is crucial to rely on recognized professionals, because a hasty implementation can lead to serious risks for the reputational and financial integrity of companies. Experts we have interviewed have emphasized this key issue. On the one hand, a business with significant capital can invest heavily in Web3.0 and can develop its own blockchain solutions to stay ahead of its competitors. On the other hand, a small business cannot do the same. With less technical and financial capital, the small business is currently only able to implement technologies that are not very advanced and whose utilization carries risks. But the situation may change rapidly in the future. Get this book and you will learn more on blockchain and decentralized finance.