Implantation is an event that occurs early in pregnancy in which the embryo adheres to the wall of the uterus. At this stage of prenatal development, the embryo is a blastocyst. It is by this adhesion that the foetus receives the oxygen and the nutrients from the mother to be able to grow. Implantation occurs approximately 9 days after ovulation, ranging between 6-12 days. (from Wikipedia)
During the week after fertilisation, your fertilised egg moves slowly down the fallopian tube and into your womb.
The fertilised egg is growing already.
Your fertilised egg attaches itself firmly to the specially thickened womb lining and this process is called implantation.
Thereafter, your fertilised egg (your baby) continues to grow and the womb expands to accommodate the growing baby.