Gene therapy is a potential mode of treatment for a wide variety of diseases caused by genetic mutations. While it has been an area of diverse and intense research, historically, only a very few patients have been treated using gene therapy—and fewer still cured. The advent of the genetic modification technique called CRISPR-Cas9 in 2012 has revolutionized gene therapy—as well as biology as a whole—and it has recently entered clinical trials for the treatment of some diseases in humans.