Blockchain technology is being used for several different kind of use-cases. These different use-cases represent different kind of users and their interaction patterns. These different use-cases require different optimizations and integration techniques. Most of the smart contract platforms treat these use-cases exactly the same because they treat all smart contracts exactly the same. This limits the adoption and scalability of blockchains. In this session, we will learn about why different kind of blockchains are needed to solve use-case specific problems, and how Substrate and Polkadot make it possible to build and connect different blockchains.