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.