Ethereum was developed on top of Bitcoin by introducing smart contracts along with Turing-complete scripting languages such as solidity. Ethereum is a general-purpose platform for DApp development. The platform is very popular. However, Ethereum is not mature yet. Compared to Bitcoin, it is more vulnerable to hacking, since any human errors in writing a smart contract are visible to everybody. It inherited the performance issue from Bitcoin. Many initiatives are ongoing to address this scalability problem. In the next chapter, we will dive into the details of solidity, the most popular language for writing Ethereum smart contracts.