This document provides an overview of CRISPR-Cas9 technology. It defines CRISPR as DNA sequences in bacteria that contain snippets of viral DNA used to detect and destroy invading viruses. The CRISPR system contains Cas9 proteins that cut DNA at specific locations guided by RNA, and RNA guide molecules. It works by integrating viral DNA into the bacteria's CRISPR loci, which are then transcribed into RNA to guide Cas9 to cleave invading viral DNA. Applications of CRISPR include disease modeling, cancer research, and correcting mutations in human embryos.