jan 1, 1986 - Mario Capecchi and Oliver Smithies Sucessfuly Edit the Mouse Genome

Description:

Using embryonic stem cells, Capecchi and Smithies were able to edit the DNA in the stem cells and implant them back into the female mice to induce permanent genetic changes to the offspring, nicknamed "knockout mice."
This used homologous recombination which was not known to take place with synthetic DNA until this experiment. Its use proved that HR could be used to edit genes (Britannica).