By Robin Ann Smith Scientists have managed to 3D print human skin, blood vessels, ears, even a cornea from living cells. But we still can’t 3D print, say, a cornstalk or a carrot.

By Robin Ann Smith Scientists have managed to 3D print human skin, blood vessels, ears, even a cornea from living cells. But we still can’t 3D print, say, a cornstalk or a carrot.