CRISPR-Cas9 is a genetic editing technique in molecular biology to modify the genomes of living organisms, which is adapted from a naturally occurring genome editing system in bacteria. By delivering a Cas9-gRNA complex into a cell, the cell’s genome can be cut at a desired location, allowing existing genes to be removed and/or new ones added in vivo. This technology has found extensive applications in various areas, such as biomedicine, disease diagnosis and treatment, gene knockdown/activation, RNA editing etc.