This chapter examines how blockchain technology evolved beyond Bitcoin and Ethereum to improve efficiency, scalability, and interoperability. It introduces alternative consensus mechanisms such as Proof of Stake, Proof of Burn, and Proof of Authority, comparing their energy use, security, and decentralization trade-offs. You will study Layer-One solutions like DAGs and sidechains that restructure transaction processing and Layer-Two techniques such as payment channels and rollups that boost throughput. The chapter also covers interchain systems like Polkadot and Cosmos and the role of bridges in cross-chain transfers, highlighting their design and security issues. It concludes with Namecoin, an early experiment in decentralized domain naming.