Researchers at the Vienna University of Technology have produced what they believe to be the world's smallest 3D printer. This device is "about the size of a milk carton", and should cost only €1200. The resin-based printer (which solidifies each of the object's layers successively in a vat of plastic resin with LEDs) has a resolution of 0.05mm, which is much higher than many consumer-grade 3D printers.
One issue we foresee with this approach is that the build envelope is quite small. This means the device will be restricted for small objects and parts only. Perhaps this may become a favorite with jewelry designers? Game piece makers? The makers say they intend to "reduce the size of the printer", so uses may become even more constrained in the future.
Via TUWien (Hat tip to Tom)