In a pair of fluorescent-lit rooms on both sides of the Atlantic, the guinea pigs awaited their fate. They were not literally guinea pigs. Two were lightly sedated, extremely fluffy white rabbits resting on pee pads; the other was Nick Green, a sixty-four-year-old part-time administrator at the University of Cambridge who reclined, hands clasped atop his patterned sweater, on the starched sheets of a hospital bed. All three were hooked up to machines that provided a readout of their vital signs, and all three were prepared to have a syringe of manufactured blood injected into their veins.

Researchers have found a way to grow more blood cells from donated blood that could be used to supplement traditional supplies.

A woman with sickle cell disease said the possibility of lab-grown blood has given her "hope" for the future. The aim of the new research is to help those with ultra-rare blood groups who need regular transfusions.