As the most effective and popular gene-editing tool, clustered regularly interspaced short palindromic repeats (CRISPR) technology has produced a revolution in biological fundamental research, medicine and biotechnology. In this review, we describe the history of the CRISPR-CRISPR-associated protein (Cas) systems, the tools of CRISPR-Cas9, CRISPR-FnCas9/RCas9, CRISPR-Cas13 and CRISPR-Cas12a, and then some comments we need to think about.
