Imagine a world in which you are able to choose every characteristic of your child. Instead of wondering if your child will have your green eyes or your partner’s crooked nose, you can design what your baby will look like as easily as creating a stuffed toy at a Build-A-Bear workshop. You want your kid to have blue eyes? Easy. Want them to be 6 foot 4 inches tall? Not a problem.

Although we don’t have the technology to make this a reality right now, such highly controlled genetic modification is no longer crazy science fiction. It’s merely a matter of when, not if. Developmental biologist Fredrik Lanner is currently performing experiments that involve modifying the DNA of human embryos.

Lanner is the first scientist to explore how to modify healthy human embryos. His experiments focus solely on editing DNA in order to learn more about how genes regulate development in early embryonic growth. Knowing more about how these genes function will allow Lanner and other scientists to learn more about what causes infertility and miscarriages.

At the Karolinska Institute in Stockholm, Lanner uses the gene editing tool CRISPR-Cas9 to cut and alter pieces of DNA. CRISPR-Cas9 and other new technologies allow scientists to examine individual gene functions and how they work as the embryo develops.

All the embryos used are donated by couples undergoing IVF treatment. These embryos are only experimented on for the first seven days of their existence, never past fourteen days.

Having greater knowledge about how these genes work will help Lanner understand the causes of infertility and miscarriage. It could also lead to advancements in the treatment of patients with diseases such as diabetes, Parkinsons, or blindness.

When I first heard about genetically modifying healthy embryos, I thought, “What’s the matter if I want my kid to have blue eyes? That’s not going to hurt anyone.” But then I thought more about the serious implications for the human race that would occur if parents started designing their own children.

Being able to choose the specific characteristics of a human would inevitably create a genetically superior race. Not everyone would be able to afford the expensive procedure to modify DNA, creating, as Lanner says, a “world of genetic haves and have-nots.” Social inequalities would only worsen, and the more genetically advanced would exert complete superiority over their economically and biologically inferior counterparts.

Scientists are also worried about creating permanent and irreversible changes that will forever affect future generations. This could include accidently introducing an incurable disease into the gene pool that could be passed down for generations.

Although Lanner’s work focuses strictly on studying the early development of embryos, many worry that it is the beginning of a slippery slope that will open the door to “designer babies.” The moral and ethical issues that these babies would provide are very complicated.

Humanity is approaching a time when all of this will be possible, and the world must decide where to draw the line. It is crucial that the leaders of science and ethics join together to come up with a set of rules that will shape a rational, controlled future for genetically engineered embryos.