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Blood transfusions save lives, but supply doesn’t always meet demand, which can lead to fatal consequences. Soon, we will be able to end that problem by making blood in the lab on demand, with no donors required.

Transfusions depend on armies of donors and complex networks for collecting and storing donated blood. Some countries are unable to build the infrastructure required to do this. Even in developed nations, hospitals can run short of supplies for people belonging to particular blood groups.

Such problems would be solved if we had a way to make effective artificial blood. One …