Scientists have grown human eggs in a laboratory for the first time - a breakthrough that could have huge implications for fertility treatment.
Egg cells were removed from ovary tissue at their earliest stage of development and grown to a point ready for fertilisation, according to a study published in Molecular Human Reproduction.
The development could help women undergoing harmful treatment, such as chemotherapy, allowing immature eggs to be recovered from patients, matured in a lab and stored for future fertilisation.
Scientists have previously matured human eggs from the late stage of development, however the fresh study is the first time a human egg has been developed in the laboratory from its earliest stage.
Scientists will next evaluate the health of the eggs and whether they are viable for fertilisation.
"Being able to fully develop human eggs in the lab could widen the scope of available fertility treatments,” said lead researcher Professor Evelyn Telfer, of the University of Edinburgh's school of biological sciences.
"We are now working on optimising the conditions that support egg development in this way and studying how healthy they are.
"We also hope to find out, subject to regulatory approval, whether they can be fertilised."
Professor Daniel Brison, of the department of reproduction at the University of Manchester, said: "This is an exciting breakthrough which shows for the first time that complete development of human eggs in the laboratory is possible, more than 20 years after this was achieved in mice.
"As the authors acknowledge, there is much more important research still to do, but this could pave the way for fertility preservation in women and girls with a wider variety of cancers than is possible using existing methods."
But Professor Simon Fishel, founder and president of leading IVF treatment providers CARE Fertility, said further research was needed to establish whether eggs developed using the method could be healthy.
He said: "This study demonstrates that there is much laboratory research to be undertaken before we can be encouraged to believe that we will achieve healthy normal eggs for clinical purposes in vitro developed follicles derived from human ovarian cortical tissue."