Those of you passionate about 3D printing have probably dealt with delta robots in the past. The milliDelta is a millimeter-scale delta robot developed by researchers at the Wyss Institute and Harvard SEAS that can be used for micro-assembly and tremor cancellation in microsurgery.
Three independently controlled piezoelectric bending actuator are used to power this. The robot measures 15mm x 15mm x 20mm, precise to ~5µm. The above video shows it in action.