Science may one day give us a way to replace damaged and diseased parts of the body with artificial replacements – but reproducing organs and tissues in the lab isn’t easy.

That’s especially true for networks of blood vessels, which at the level of fine, thread-like capillaries are microscopic – these capillaries can be as small as 0.005 millimeters (34 times thinner than a human hair), and only let blood cells through in single file.

Researchers led by a team from MIT have now published a study in PNAS that details a way of engineering blood vessels in the lab with significantly greater precision than before.