Scientists have succeeded in making early-stage sperm from human skin tissue, giving infertile men a shot at fathering children that are genetically their own.
The breakthrough could also lead to new contraceptives and a "miracle pill" to treat infertility.
However, the science is also fraught with moral and ethical concerns. Critics argue it's wrong to meddle with the building blocks of life and warn of a future in which babies are created through entirely artificial means.
Scientists have already succeeded in coaxing embryonic stem cells - master cells plucked from embryos in their first days of life - into turning into sperm. But using skin as a starting point would be more ethically acceptable. It would also mean the sperm would have the man's genes.
The American scientists used a cocktail of chemicals to wind back the "biological clock" in skin cells, turning them into cells with the chameleon-like qualities of embryonic stem cells.
They then used a combination of nutrients to coax them to developing into round cells which were just a few steps away from mature sperm and appeared genetically normal.
The University of Pittsburgh School of Medicine team, led by Dr James Easley, believe they have cracked the most difficult part of sperm development. This means that by tweaking the procedure it should be relatively easy to get to the next stage - elongated cells that, while yet to grow tails, should be able to fertilise eggs.
The technique is still many years away from use in clinics and, as the law stands, lab-grown sperm are banned from use. But in the shorter-term, the breakthrough, detailed in the journal Cell Reports, could lead to new infertility drugs and contraceptives.
All of the early-stage sperm were made from male skin samples. Attempts at using female skin failed, suggesting men will always have an important role in the creation of life.
Other research teams are trying to make eggs from women's skin, raising the possibility of eggs and sperm being used to create children through entirely artificial means.
- DAILY MAIL