Human eggs and sperm have been grown in the laboratory in research which could change the face of parenthood.
It paves the way for a cure for infertility and could help those left sterile by cancer treatment to have children who are biologically their own.
But it raises a number of moral and ethical concerns. These include the possibility of children being born through entirely artificial means, and men and women being sidelined from the process of making babies.
Opponents argue that it is wrong to meddle with the building blocks of life and warn that the advances taking place to tackle infertility risk distorting and damaging relations between family members.
The U.S. government-funded research also offers the prospect of a ‘miracle pill’ which staves off the menopause, allowing women to wait longer to have a child.
It centres on stem cells, widely seen as a repair kit for the body.
Scientists at Stanford University in California found the right cocktail of chemicals and vitamins to coax the cells into becoming eggs and sperm.
The sperm had heads and short tails and are thought to have been mature enough to fertilise an egg.
The eggs were at a much earlier stage but were still much more developed than any created so far by other scientists.
The double success, published in the journal Nature, raises the prospect of men and women one day ‘growing’ their own sperm and eggs for use in IVF treatments.