Final answer:
A blastocyst attaches to the lining of the uterus.
Step-by-step explanation:
After fertilization, a blastocyst attaches to the lining of the uterus. The blastocyst is a hollow ball of cells that forms from a fertilized egg, and it implants itself into the thickened uterine lining, which is prepared to receive and nourish the developing embryo.
Learn more about Implantation of blastocyst