Fertilised IVF embryo. Computer illustration of a dividing fertilised egg cell, into which a sperm cell has been injected during an in vitro fertilisation (IVF) procedure. The injected sperm cell fertilises the egg cell to form a zygote, which has genetic material from the mother and father. The cell then divides several times to form a ball of cells in the first stage of embryonic development. It is then placed in the uterine wall, allowing pregnancy to proceed as normal.