Blockchain technology is the first successful Bitcoin Network. It enables the ledger to become more decentralized and secure. Since it is not limited to bitcoin and controlled by third parties by government, corporations, or banks, the technology is capturing several industries, including cryptocurrency, infrastructure& hardware, financial technology, Internet & mobile and so on. Blockchain is used as a public ledger to verify all peer-to-peer system transactions and maintain traded bitcoin spending from central authorities while bitcoin has distributed transactions. Achieving high Blockchain-based performance and privacy & security are global issues that are desire to be overcome as claims show they are still significant challenges in many Blockchain applications. This paper presents an introduction to Blockchain and the process of this technology in the way of outlining Blockchain types. Also, recent advances, challenges, real economy integration, and current situations of this technology have been listed.

Background and Objectives: Blockchain technology as a distributed and tamper-proof data ledger is attracting more and more attention from various fields around the world. Due to the continuously growing of the Blockchain in both transaction data and the number of nodes joining the network, scalability emerges as a challenging issue. Methods: In this survey, the existing scalability solutions in the Blockchain are discussed under five categories including on-chain scalability, off-chain scalability, scalable consensus mechanisms, DAG-based scalability, and horizontal scalability through sharding. Meanwhile, the novelties they have created on the fundamental layers of the Blockchain architecture are investigated.Results: As a result, the advantages and disadvantages of the discussed mechanisms are pointed out, and a comparison between them in terms of different scalability metrics such as throughput, latency, bandwidth, and storage usage is presented. Therefore, this study provides a comprehensive understanding of the various aspects of Blockchain scalability and the available scalability solutions. Finally, the research directions and open issues in each category are argued to motivate further improvement efforts for Blockchain scalability in the future.Conclusion: Scalability allows Blockchain system to sustain its performance as it grows up. Lack of scalability has a negative effect on the mass adoption of the Blockchain in practical environments. This paper presents a profound analysis of the existing scalability solutions, the issues and challenges they address, and the ones that are not resolved yet. Consequently, it inspires novel ideas for more scalable and efficient Blockchains in the future.

Dear Editor, Nowadays, healthcare has been faced with different technologies that promise new advantages for better and more advanced healthcare. Blockchain is taken into consideration as one of the emerging technologies, which there are great interesting. According to Gartner, Blockchain is classified as one of the top ten strategic technology trends in 2020. 1 In current systems, a thirdparty control the transaction between requester and provider. For example, in the internet-based purchasing, the bank controls the financial transaction between customer and seller. In other words, there is a centralized control on the transactions, and consequently, the data is stored in the centralized database...