Scientists have found how to mass produce blood. The blood is good enough to give to people. The old way of making blood was very slow and expensive. It was difficult to make a lot. The new way means scientists can make a lot. They can make as much as they want. They can make "unlimited" amounts of blood.

A researcher said his team needs the technology to mass produce blood. He said it was a challenge. He said his team would make only rare types of blood at first. These are not easy to find. Not many people with rare blood types donate blood. He said: "Suitable…red blood cell donations can be difficult to [find]."