Blood that has been grown in a laboratory has been put into people in a world-first clinical trial, UK researchers say.
Tiny amounts – equivalent to a couple of spoonfuls – are being tested to see how it performs inside the body.
The bulk of blood transfusions will always rely on people regularly rolling up their sleeve to donate.
But the ultimate goal is to manufacture vital, but ultra-rare, blood groups that are hard to get hold of.
These are necessary for people who depend on regular blood transfusions for conditions such as sickle cell anaemia.
If the blood is not a precise match then the body starts to reject it and the treatment fails. This level of tissue-matching goes beyond the well-known A, B, AB and O blood groups.
Prof Ashley Toye, from the University of Bristol, said some groups were “really, really rare” and there “might only be 10 people in the country” able to donate.
At the moment, there are only three units of the “Bombay” blood group – first identified in India – in stock across the whole of the UK.