The idea of designer babies has been a topic of discussion for a while, but the technology to bring that science fiction to reality is finally here. The technology is called CRISPR Cas9. This technology has the ability to alter the DNA sequence of any organism by removing sections from the genome. This in turn triggers a cell repair response that eventually changes the outcome of that organism. In the context of designer babies, scientists can use this technique on an embryo and manipulate the DNA to cause a specific outcome: blue eyes or brown hair.
The process CRISPR Cas9 uses is actually a naturally occurring process that scientists have been able to mimic. Naturally, bacteria will implement this splicing process to fight off viral infections by splicing the DNA and then repairing itself. Scientists were able to watch, learn, and mimic this process and use it to their own advantage.
For now, the technology will allow scientists to implement the process for eye and hair color and even height. With continued research, this technology will move closer to being able to eliminate diseases as well and save afflicted embryos before the child is even born.