Never mind 3D-printing organs -- the real dream is to make the tissue itself bend to your will, and UCSF scientists have managed just that. They've discovered that they can 'hack' special cells that help fold tissue (mesenchymal cells) to create 3D shapes out of live tissue. The trick is to lay out these cells in specific patterns that "tug" on other cells' extracellular matrix fibers. You can create surprisingly diverse items, ranging from simple bowls and ripples to decidedly unnatural items like cubes and coils.
There's plenty of work to be done. The researchers want to combine their shape forming work with other discoveries into tissue patterning, and they need to understand how cells change in response to this folding.
The practical implications are already evident, though. This could lead to lab-made organs that are designed to exact specifications using the natural processes of the cells themselves. You could also see soft robots created largely from living material rather than inert substances like rubber. It's a tad creepy (imagine robots that can grow), but it could also dramatically expand what's possible in medicine and machinery.