  Blockchain, as the basis for cryptocurrencies, has received extensive
attentions recently. Blockchain serves as an immutable distributed ledger
technology which allows transactions to be carried out credibly in a
decentralized environment. Blockchain-based applications are springing up,
covering numerous fields including financial services, reputation system and
Internet of Things (IoT), and so on. However, there are still many challenges
of blockchain technology such as scalability, security and other issues waiting
to be overcome. This article provides a comprehensive overview of blockchain
technology and its applications. We begin with a summary of the development of
blockchain, and then give an overview of the blockchain architecture and a
systematic review of the research and application of blockchain technology in
different fields from the perspective of academic research and industry
technology. Furthermore, technical challenges and recent developments are also
briefly listed. We also looked at the possible future trends of blockchain.
