Abstract The nature of clones is discussed along with the origin and principles of the concept that human and other mammalian clones can be produced. The physical and chemical properties of living cells are described and it is shown these properties place severe limitations on attempts to bring human and mammalian clones into being. The observed result of such attempts that a large number of distorted and aborted foetii have been produced is demonstrated to have been predictable. Offspring produced by such attempts cannot be classified under any of the normal classifications of human relationships e.g. son, daughter, brother, sister or twin and that such offspring are entirely unnatural and likely to be metabollically unstable. It is concluded that the cloning of humans and other mammals is difficult, certainly dangerous and perhaps impossible.