Bioinformatics, the study of integrating high throughput biological data and statistical model through intensive computation, has been attracting great interest in recent times and Sequencing is at the very center of it. The large amount of information obtained from sequencing has deepened our understanding and fundamental knowledge of organisms. This review will aim to provide a brief summary of new sequencing technology, current issues, and projects focused on medical applications. The article is organized in three parts. Part I explains common terminologies and background of sequencing technology, and Part II compares distinct features of currently available platforms. Part III contains applications in various medical fields.