According to He Jiankui, the goal of his work was not to prevent an inherited disease in babies, but to bestow them with a trait to resist any possible future infection with HIV.
He Jiankui, largely unknown until yesterday, is an associate professor at Shenzhen's Southern University of Science and Technology of China (南方科技大学 or SUSTC).
The technology to genetically edit human embryos has been around for a while, but scientists were unwilling to cross that ethical line.
According to the AP, a US scientist had helped with the project but said that this sort of DNA editing is banned in the States due to risks that could be passed down for generations.
CRISPR is a molecular tool that allows scientists to edit sections of DNA. "I think this is justifiable", Harvard geneticist George Church said, calling HIV "a major and growing public health threat".
Altering genes in sperm, eggs or embryos means those changes can be passed down to future generations - people who would have no way to consent to those changes. He said twin girls with the altered genes were born earlier this month.
In his talk, which detailed his research on editing a gene called CCR5 in human embryos, He said that the parents were given the option to exit the trial without implanting the gene-edited embryos, or to use non-edited embryos instead.
Scientists sharply criticized He's work and many institutions distanced themselves from him. It forms something of a protein doorway which allows HIV to enter a cell, eventually reproduces rapidly and take over the immune system.
The gene-editing of babies is seen by some as a slippery slope to enhancements or designer children.
The Second International Summit on Human Genome Editing begins in Hong Kong on Tuesday, Nov. 27, and He is expected to make an appearance at the event. Given our current level of knowledge, editing the genome of healthy embryos to attempt to confer resistance to HIV is completely unethical'.
"The university will call for worldwide experts to form an independent committee to investigate this incident, and to release the results to the public", the statement said. The university, in which Jiankui worked at, issued a statement that officials were "deeply shocked" by the experiment, stressing it was conducted elsewhere.
"If true, this experiment is monstrous", he told Reuters.
However, his work - a byproduct of personal ambition and a vague regulatory environment in a country that has been pushing ahead in the field of gene editing for years - did not come as a total surprise to everyone.
Kiran Musunuru is a University of Pennsylvania gene editing expert and editor of a genetics journal.
"This work is a break from the cautious and transparent approach of the global scientific community's application of CRISPR-Cas9 for human germline editing", Jennifer Doudna, a biochemist at the University of California, Berkeley, said in an interview.
But this is not the first time Chinese researchers have experimented with human embryo technology, and last September scientists at Sun Yat-sen University in China used an adapted version of gene-editing to correct a disease-causing mutation in human embryos. In the research, says JK, 16 out of 22 embryos were edited. The CCR5 gene, for example, affects the functioning of white blood cells and a person's vulnerability to the West Nile virus.