Application of genome editing have garnered a lot of attention in the scientific world. Its ability to make permanent and precise modification or ‘edits’ in the genomic DNA sequences have open up the possibility of probing the functionality of genes and correcting abnormal genes to treat genetic diseases. The CRISPR/Cas9 which was adapted from Type II bacterial adaptive immune system is the most applied genome editing system due to the ease and efficiency of the system in customising the nucleases needed in editing the targeted sequences. However, the downside of this system is the high frequency of ‘off-target’ editing caused by the nature of the Cas9 protein that can tolerate mismatches between customised nucleases; sgRNA, and the genomic sequences. Despite the set-back, researchers continue applying CRISPR/Cas9 system to edit the genome by minimising the frequency of ‘off-target’ edits. Application of the improved system had successfully produced numerous results in the initial treatment of genetic diseases such as cystic fibrosis, β-thalassemia, and Duchenne Muscular Dystrophy. The fast-paced development and improvement made to this system will continue to be utilised by the researchers around the world for the treatment of human diseases, a progress much needed and awaited.