The first cows were cloned by separating one cell from a developing cow embryo and, using electricity, fusing it to a donor cell. The cow embryo cell had the nucleus, which contains DNA. When the fused cell started dividing, the resulting mass of cells had nuclei with the cow DNA.
After the fused embryo had sufficiently divided in its Petri dish, it was transferred to the womb of a cow. The result was two cloned calves, named Fusion and Copy. The process, called nuclear transfer, was first tried on sheep in 1984 by scientist Steen Willadsen. In 1987, Neal First, Randal Prather and Willard Eyestone used the method for cloning cow embryos. The cloning was a form of in vitro fertilization, which at the time was being used as a fertility option for couples unable to conceive normally.
Further experiments were carried out, using cells from adult animals for cloning. Though the method had viability issues, it did create the famous sheep Dolly. In 1998, several groups of scientist used this new method, somatic cell nuclear transfer, successfully to clone cows. They also experimented with combining fetal and adult cells, successfully creating the first male clone, but it was a mouse.