RChain breaks the impossible triangle by being the only leaderless blockchain that allows for safe and atomically concurrent execution of smart contracts within and across shards. RChain is the only leaderless smart contract platform that can safely execute smart contracts concurrently in a single shard, enabling linear scaling. This feature is the culmination of more than 30 years of research in concurrency and process computing. RChain solved many problems that plagued the development of the public chain through the revolutionary Rho calculus, making it possible for the first time to compute the chain in general. Fast conflict detection based on Rho algorithm and Casper CBC consensus, all nodes can reach consensus by sending blocks together, achieving single-fragment scalability for the first time, enabling big data to be directly linked without using IPFS. Inter-shard synchronization consensus based on Rho calculation ensures atomicity of cross-shard contract calls, making inter-shard interaction and collaboration seamless for the first time. The behavior type system based on Rho calculus can complete the fast formal verification under concurrent and sharding, and complete the safe and orderly arrangement of a large number of contracts on the chain. Its unique reactive contract is better suited to high-frequency application scenarios such as DeFi than traditional active contracts. RChain's unique technology approach makes it the perfect choice to build the world's computers.