A clone is a group of organisms that derive from a single ancestor and are genetically identical. A clone can be a group of mammals such as sheep, or a group of cells in culture.

Cloning cells is a powerful tool in biology and medicine, since growing large quantities of identical cells allows for a large harvest of the various identical and useful components of these cells. It is possible to construct genetic components in the laboratory, place them in cells, and then have the cells grow and multiply to produce large quantities of the components.

Cloning is an essential technique in modern molecular biology; it is used widely in studying genetic effects in the drug-abuse field. Cloning much larger organisms such as cows and sheep is expected to have a major impact in that production of the best of any species can theoretically be accomplished by cloning. This is an important goal in agriculture today.