Genome editing had a long history before the appearance of CRISPR. Although a decade has passed since the initial use of CRISPR with mammalian cells, the first attempts at gene editing occurred in the 1980's. Subsequently, many researchers tried to develop methods to edit specific genes. Here, we review the history of genome editing and improvements in genome editing tools. In the last two decades, genome editing tools have been applied in basic sciences, the bio-industry, and therapeutics. We provide examples in which genome editing tools have been applied to various tasks. Recently, new CRISPR-Cas techniques, such as base and prime editing and anti-CRISPR proteins, have attracted considerable interest. Accordingly, these topics are also reviewed.