This article explores the evolution, working principles, applications, challenges, and future prospects of blockchain technology and cryptocurrencies. It begins by explaining blockchain as a decentralized, secure, and transparent ledger system that powers digital currencies like Bitcoin and Ethereum. The article highlights key features of blockchain, including decentralization, immutability, and security, while also discussing how cryptocurrencies operate without intermediaries. Key applications of blockchain include decentralized finance (DeFi), smart contracts, non-fungible tokens (NFTs), cross-border payments, and supply chain management. However, the technology faces challenges such as scalability issues, regulatory uncertainty, security risks, and environmental concerns due to energy-intensive consensus mechanisms. Looking ahead, layer-2 scaling solutions, central bank digital currencies (CBDCs), blockchain integration in traditional finance, and sustainable blockchain models are expected to shape the future. Despite hurdles, blockchain and cryptocurrencies continue to revolutionize finance, digital ownership, and various industries, with ongoing innovations paving the way for broader adoption.