It’s an achievement that is sure to set of fierce debate in both the scientific world and the public: a Swedish scientists has started editing the DNA in healthy human embryos, which could help us learn how to prevent miscarriages and treat infertility … or lead to playing god and creating designer babies, if you believe the critics.

Developmental biologist Frederik Lanner is the first known researcher to actually try to alter the genes of human embryos that are healthy, which many consider an ethical taboo. Lanner also wants to help scientists learn mroe about stem cells from embryos so they could be used to treat diseases.

But others are worried that this discovery will allow people to start creating “designer babies,” or babies whose DNA has been altered to remove undesirable traits.

But Lanner says that’s not his goal. He just wants to study the embryos for the first seven days of their growth and won’t let them develop beyond two weeks. He says that the benefits far outweigh any risk.

The purpose of Lanner’s office, according to their website, is to: “Explore treatment of age-related macula degeneration using ESC derived retinal pigmented epithelial cells. ESCs isolated from the human blastocyst can be propagated indefinitely and directed into any cell type of the adult human, offering great potential for regenerative medicine to replace lost or damaged tissues. The knowledge of how these pluripotent cells are established and controlled in vivo is generated primarily in animal modes such as the mouse while our knowledge of the same process in the human is rudimentary and key differences are emerging. We will explore these issues through single cell mRNA sequencing, pioneering genetic technologies and functional assays in human blastocysts. This fundamental knowledge will also be important for our understanding of infertility, a problem affecting 10-15% of all couples in our society.”