Implantation happens when the fertilized egg, the blastocyst, has completed its travel through the fallopian tube and attaches to the lining of the uterus. The blastocyst is a cluster of tiny cells, smaller than the head of a pin.
Implantation happens on average nine days (6-12 days) after ovulation and fertilization.
Some women report having around that time implantation symptoms like implantation cramps, implantation bleeding or implantation cramping.
Implantation bleeding usually consists of a couple of drops of blood, which can be either red or brown. If the bleeding is heavier more like a period, then it's unlikely implantation bleeding.
Most pregnant women, however typically have little to no symptoms on the day of implantation and do not experience typical implantation bleeding, while some women who are not pregnant may experience some spotting which they believe could be implantation.