This chapter provides a comprehensive introduction to blockchain technology, establishing the foundation for understanding adaptive and scalable blockchain protocols. It begins with an in-depth examination of blockchain’s fundamental components, including block structure, transaction processing, and state management. Then, the chapter explores essential cryptographic technologies underlying blockchain systems, such as hash functions, Merkle trees, digital signatures, and zero-knowledge proofs. Network architecture and communication protocols are detailed, with particular emphasis on peer-to-peer networks and data propagation mechanisms. Next, current scalability limitations are analyzed from multiple perspectives: physical resource constraints, system design limitations, and fundamental trade-offs in the blockchain trilemma. The chapter concludes by highlighting the pressing need for adaptive blockchain solutions, examining how different applications require varying performance characteristics and how transaction demands fluctuate over time.