system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: After invitro eggs are fertilized, are they kept at a certain temperature to grow before implanted? How does the lab part work?
gpt
They are incubated under optimal conditions (the correct Temperature, Oxygen levels and nutrients) , usually until a blastula is formed. at this point a cell can be removed for genetic analysis (also called  Preimplantation Genetic Diagnosis  or PGD) and the embryos can be frozen in liquid nitrogen until needed.