It's long been a scientific dream: to give people a special vaccine before birth to prevent them from getting terrible illnesses. Gene editing (基因编辑) is one way in which we could do this. But this method has also created some discussion.

In an online video posted on Nov.26, 2018, He Jiankui, a researcher at the Southern University of Science and Technology, said that he had helped to make the world's first genetically edited babies.

The babies are twin girls who were born in November. Their father had HIV. The twins' genes were edited in order to prevent them from suffering from the HIV virus.

He said he chose to do this because HIV is widespread in China. "I feel such a strong duty not only to be the first to do this, but also to set an example, " he told AP.

But his actions caused many questions. Although gene editing may help to prevent disease, many people are wondering if it is safe and ethicalto use it on humans.

Some believe that gene editing could be useful to HIV patients. HIV is "a large and growing public health problem", according to Harvard Medical School genetic professor George Church. Using gene editing for HIV is "a good idea", Church told AP.

However, others think that gene editing is still in its experimental periods and could result in terrible changes. "It could cause genetic problems later in life, including the development of cancer, " Julian Savulescu from the University of Oxford told BBC News.

Others fear that people might use gene editing technology to make "designer (设计的) babies". It would give parents the ability to choose everything from their baby's eye colour to their IQ.

"You could find wealthy parents buying the latest 'upgrades' for their children, leading to even greater unfairness than we already live with, " Marcy Darnovsky, director of the San Francisco Center for Genetics told BBC News.