In what may be a critical breakthrough for creating artificial organs, Harvard researchers say they have created tissue interlaced with blood vessels.

Using a custom-built four-head 3-D printer and a “disappearing” ink, materials scientist Jennifer Lewis and her team created a patch of tissue containing skin cells and biological structural material interwoven with blood-vessel-like structures. Reported by the team in Advanced Materials, the tissue is the first made through 3-D printing to include potentially functional blood vessels embedded among multiple, patterned cell types.