Lulu and Nana are two baby girls born in China. Their story got very famous because when they were in their mother's tummy, some scientists changed their genes.
Now, genes are like instructions that tell our body how to grow and work. Some of these genes can have problems, and that's why scientists study them to see if they can change them and make people's lives better.
So, these scientists changed Lulu and Nana's genes to protect them from getting sick when they grow up. They did this by "cutting" some genes out and putting in some new ones. This is called gene editing.
But, not everyone was happy about this. Some people thought that the scientists were playing with nature and that they might have been doing something dangerous that could hurt the babies or even their future children.
So, while Lulu and Nana might now be protected from some illnesses, there are still a lot of questions to answer about gene editing, and people are trying to figure out how to make sure that it is safe for everyone.