For decades researchers have chased the Philosopher’s Stone of a hygienic, endless supply of blood that could be mass manufactured. Stem cell technologies may have provided a breakthrough. Researchers at the University of Edinburgh announced this spring that its $8.3 million project had produced a small supply of blood derived by culturing stem cells in biochemical conditions similar to those in bone marrow.

The next steps involve the transfusion of tiny amounts of the substance—four or five milliliters each—into three healthy adult volunteers in 2016. But even if this trial succeeds, the group faces many challenges, including how to scale up its efforts. Using current methods, making a unit of the artificial blood would cost more than $5,000, which dwarfs the current cost of several hundred dollars for a unit of donor blood.