A miniature liver measuring just an inch in diameter has been grown using human cells by scientists at the University of Wake Forest.
The liver, however, is not big enough to work for a human.
But scientists hope that someday it would grow bigger livers for people who need them, or to use them for testing new drugs.
To engineer the organs, the scientists used animal livers that were treated with a mild detergent to remove all cells, leaving only the collagen "skeleton."
They then replaced the original cells with two types of human cells: immature liver cells known as progenitors, and endothelial cells that line blood vessels.
It's the first time human-rather than animal-cells have been used to engineer livers in a laboratory setting.
"Our hope is that once these organs are transplanted, they will maintain and gain function as they continue to develop," CBS News quoted lead author Pedro Baptista, as saying.