3D printing a human heart using a patients own cells:

From a human ear, to perfectly functioning valves, 3D printers are already being used in many areas of surgery and medicine, but now scientists in the U.S. are attempting to build a whole human heart using the versatile piece of kit. Their ultimate goal is to create a new heart for a patient using their own cells that could be transplanted. 
It is an ambitious project to first make a heart and then get it to work in a patient and it could be years – perhaps decades – before a 3D printed heart would be put in a person in a standard operating theatre. The technology, though, is not all that futuristic.
Researchers have already used 3D printers to make splints, valves and even a human ear. So far, the University of Louisville in Kentucky has printed human heart valves and small veins with cells, said Stuart Williams, a cell biologist leading the ambitious project.
They have also successfully tested the tiny blood vessels in mice and other small animals and Professor Williams believes scientists will be able to print parts and assemble an entire heart in three to five years. The finished product would be called the ‘bioficial heart’ – a blend of the natural and artificial.