LentiCRISPR/Cas9-V2 is one of the most popular gene-editing and knockout (KO) tools. The lentiviral vector V2mO (CRISPR/Cas9-V2-mOrange) added a visual marker for the easy monitoring of lentiviral production, transduction efficiency, and cell sorting. It provides the estimation of gene editing efficiency by simple calculation of aberrant cells from total cells based on a PCR electropherogram from a cell pool, and it also details a method of gene rescue by overcoming Cas9 editing to KO essential genes, doxycycline-inducible (Dox) lentiviral systems may be used to maintain transduced cells viable while Dox-induced treatment is used to study downstream effects in genes of interest. Low levels of Dox induction may abate Cas9 overexpression in order to reduce off-target editing. A new trend of employing RNA editing without genome alteration using Cas13, ADAR and APOBEC1 has become a hot topic, as these editing techniques may hold the promise of altering RNAs by a single nucleotide conversion or even introducing stop codons, although those systems need further improvements and discoveries.