A mouse embryo developed from stems cells has a beating heart and is starting to develop muscles, a gut and nervous system while it grows inside a lab at the University of Virginia.   

Scientists sparked development of the cells by weaving the different types together, allowing it to become 'the first in vitro model of a mammalian embryo with so many tissues to be built from stem cells,' the team shared in a press release.  

This is also the first version complete with a notochord, which is a cartilaginous skeletal rod supporting the body in all embryos and 'is a definite trait of vertebrate animals,' according to the researchers.

The team hopes the breakthrough will assist researchers with understanding mammalian development, battle diseases, create new drugs and grow tissues and organs for human transplants. 

Christine Thisse, Ph.D., of UVA's Department of Cell Biology, said in a statement: 'We found a way to instruct aggregates of stem cells to initiate embryonic development.

'In response to this controlled instruction, the aggregates develop into embryo-like entities in a process that recapitulate the embryonic steps one-by-one.

'What is amazing is that we can get the variety of tissues that are present in an authentic mouse embryo.'

The use of  stem cells has opened up a new world of science, allowing experts to use the special cells to create other cells with different functions.