A team of Australian scientists has genetically modified human embryonic stem cells to glow red when they develop into premature red blood cells.
The breakthrough is seen as the next step in producing artificial blood.
Dr Andrew Elefanty at Monash University in Melbourne and his colleagues inserted specific genes that code for colour, into the DNA of a manufactured stem cell line.
Stem cells are the template from which all cell types in the body form.
He says the coloured genes, known as 'reporters', highlight the emergence of certain cell types.
"What we've said to the stem cells is when you''re going to turn on the gene for globin we want you to also turn on a red light," ABC Science quoted Elefanty as saying.
He says fluorescing cells are a useful tool to help work out the best way to engineer specific cells.
"We learn what the right growth enhancing substances are that the body normally uses and we put those into the laboratory," he said.
Elefanty says fluorescing cells also allows scientists to monitor the cells when they've been injected into animals.
"Sometimes it's not that easy to tell the difference between the ones you put in and the ones that were already there," he said.
The researchers are hoping the development of glowing stem cell lines will help them work out how to develop mature red blood cells faster.
However, Elefanty says they are still a way off producing artificial blood that could be used in human blood transfusions.
He and his colleagues are working with Queensland researchers to develop ways to mature the cells, but there are still many issues to resolve.
"We've got to make sure the cells are safe, that they don't keep growing and form tumours and that the immune system doesn''t reject them," he said.
The research has been published in Nature Methods.