Once this fourth division has occurred the embryo has reached a 16 cell stage.

Today surgically implanted embryos in cows have reached much higher success rates - up to 72 percent.

Human embryos reach the blastocyst stage 4-5 days post fertilization, at which time they consist of 50-150 cells.

"Project Fortune was stationed here four years ago, after the first viable embryo reached maturity," Harper said.

When the embryo reaches the eight-cell stage, a single cell is removed and tested for genetic abnormalities.

These fertilized eggs are allowed to develop until the embryo reaches a pre-determined size and are then boiled.

When the embryos reach the eight-cell stage, one cell is removed and tested genetically, a procedure called preimplantation genetic diagnosis.

When the resulting embryo reached the six-day stage, it was implanted in a ewe.

Human embryos reach the blastocyst stage 4-5 days after fertilization.

Enterocoelous development begins once the embryo reaches the gastrula phase of development.