Designer embryos. Conceptual computer artwork of designer human embryos for sale. Human embryos are an early stage of the development of a human from a fertilised egg cell. This stage lasts until the eighth week of gestation. The embryos will be less than 10 centimetres long, and will weigh less than 50 grams. Developments in technologies such as human cloning and genetic engineering could one day allow people to select the embryos they want from a range of available choices. This could even lead to embryos being treated as products to be sold in a sale: Buy one, get one free!!" There are many moral and ethical objections to this."