Gene editing technology has been at its mature stage with the successful development of TALENs and CRISPR/Cas enzymes. The genetically modified endonucleases of ZFNs, TALENs, and CRISPR/Cas are widely used in the development of genetically modified cells or organisms. Among the enzymes that possess gene editing ability, CRISPR/Cas is the latest member with high efficiency in gene editing and simplicity in cloning. This review discusses the discovery of CRISPR, the development of the CRISPR/Cas system, and its applications as a new gene editing system.