'Designing' babies originally started with the process of In-Vitro Fertilisation (IVF)
Fertility researches developed another process called Pre-implantation Genetic Diagnosis (PGD) in order to screen embryos before implanting them in the mother.
In PGD, the embryo is removed from a woman and is manipulated in a lab to have certain desired qualities, and then placed back into the female's womb to finish development.