A joint team of researchers from the US and the UK have for the first time created a synthetic human embryo-like structure from stem cells, without eggs and sperm.
The structures do not have a beating heart or a brain, but have cells which can later form the placenta, yolk sac and the embryo itself, The Guardian reported.
The finding may pave the way for understanding of genetic diseases or the causes of miscarriages.
Professor Magdalena Zernicka-Goetz from the University of Cambridge, UK and also a professor of biology and biological engineering at California Institute of Technology (CalTech), US, developed the embryo model using stem cells - the body's master cells, which can develop into almost any cell type in the body.
"We can create human embryo-like models by the reprogramming of [embryonic stem] cells," said Zernicka-Goetz while presenting the research at the International Society for Stem Cell Research's annual meeting in Boston on Wednesday.
In August, last year, Zernicka-Goetz and her team, along with Israeli researchers, had described creating model embryo-like structures from mouse stem cells. Those "embryoids" showed the beginnings of a brain, heart and intestinal tract after about eight days of development.
Meanwhile, Zernicka-Goetz said that the embryos were cultivated at a stage just beyond the equivalent of 14 days of development for a natural embryo, the report said. The research is yet to be published in a journal.
Each structure of the model was grown from a single embryonic stem cell. It reached the beginning of a developmental milestone known as gastrulation -- when the embryo transforms from being a continuous sheet of cells to forming distinct cell lines and setting up the basic axes of the body.
At this stage, the embryo does not yet have a beating heart, gut or beginnings of a brain, but the model showed the presence of primordial cells that are the precursor cells of egg and sperm, the report.
"Our human model is the first three-lineage human embryo model that specifies amnion and germ cells, precursor cells of egg and sperm," Zernicka-Goetz was quoted as saying to The Guardian.
"It's beautiful and created entirely from embryonic stem cells."
The research also raises serious ethical and legal issues as the lab-grown entities fall outside current legislation.
"Unlike human embryos arising from In Vitro Fertilisation (IVF), where there is an established legal framework, there are currently no clear regulations governing stem cell-derived models of human embryos, James Briscoe, Associate Research Director at the Francis Crick Institute, said in a statement.
"There is an urgent need for regulations to provide a framework for the creation and use of stem cell-derived models of human embryos," he added.