Scientists say they have managed to create an artificial structure resembling a mouse embryo, in what is a world first.
The new discovery could help them to understand the early stages of embryo development and how it can go wrong in humans.
Researchers at the University of Cambridge used a combination of genetically modified mouse cells together with a 3D scaffold known as an extracellular matrix, and were able to grow a structure capable of assembling itself.
The structure develops and looks very much like the natural embryo, and the findings have been published in the journal Science.
Previous attempts to create embryo-like structures have had limited success, because early embryo development requires different types of cells to coordinate closely with each other.
While the artificial embryo closely resembles the real thing, it is unlikely to develop further into a healthy foetus.
"Both the embryonic and extra-embryonic cells start to talk to each other and become organised into a structure that looks like and behaves like an embryo," explains Professor Magdalena Zernicka-Goetz from the Department of Physiology, Development and Neuroscience, who led the research.
"We think that it will be possible to mimic a lot of the developmental events occurring before 14 days using human embryonic and extra-embryonic stem cells using a similar approach to our technique using mouse stem cells.
"We are very optimistic that this will allow us to study key events of this critical stage of human development without actually having to work on embryos. Knowing how development normally occurs will allow us to understand why it so often goes wrong."