CAMBRIDGE (REUTERS) - On the right, the embryo of a mouse, on the left, an artificial copy - grown in the lab.
Its synthetic structure is very similar to the real thing - although it is the product of just two of the three different kinds of stem cells nature needs.
Cambridge University researchers say although it was known that stem cells interact with each other, the extent of that partnership was a shock.
"We were incredibly shocked, we were very surprised when we found out that those stem cells that we put together in contact with another type of stem cells they can self assembly so quickly and so perfectly...after three days of co-culture those cells are getting the right information of what they should become," said Professor Magdalena Zernicka-Goetz.
"So this was quite incredible and despite that we know that these cells are magical, stem cells are magical in their powerful potential of what they can do, we didn't realise that they are able to self-organise to this extent so beautifully, so perfectly."
The team insists their breakthrough cannot become a healthy foetus and called suggestions the research would lead to the growth of human cells "deeply upsetting."
"First of all we do not generate those structures with human cells but with mouse cells and we don't even plan to generate artificial mice in the lab. It's impossible. We look at the process of development that takes place within the first few days of the time of implantation, so it's far away from building even one single organ." said Prof Zernicka-Goetz.
The discovery may mean fewer mouse or human embryos are needed for research and could help explain why so many human pregnancies fail in this early stage of development.