But what if doctors could grow new organs on demand from a patient's own cells? In a major step towards this future, scientists from the University of Texas Medical Branch (UTMB) have now transplanted bioengineered lungs into pigs, with no complications arising from the procedure.

Instead of waiting for another person to offer up a spare organ, in the future patients could simply have whatever they need grown or even 3D-printed from their own cells. In recent years, scientists have managed to make strides towards this by bioengineering muscle, blood vessels, kidneys, bone marrow and skin.

Now, the UTMB researchers have implanted an entire lung into pigs, grown from their own cells. To start with, they took a lung from another animal and bathed it in a solution designed to strip out all the blood and living cells. What's left is a "scaffold" of proteins in the shape of the lung.