"The zygote is a single cell and contains the genetic blueprint to direct the next complex steps to become the embryo and fetus," says What to Expect Medical Review Board Member Aaron K.

This produces a new cell called a zygote, which will mature into an embryo. The number of cells increase by mitosis, and as the embryo develops, the cells begin to differentiate (or specialise).

After a sperm fertilizes an egg, the totipotent cell divides into a zygote. As division continues, some cells divide into the growing mass, distinguishing cells that form the embryo (epiblast) from ...

The fusion of sperm and egg gametes during human fertilization establishes a diploid zygote and initiates a series of cell divisions that result in a multicellular embryo. The blastocyst stage is ...