Optomechanics is a crucial part of any microscope; when working at high magnification, it is absolutely crucial to keep the sample steady and to be able to bring it into focus precisely. Accurate motion control is extremely difficult using printed mechanical parts, as good linear motion typically equires tight tolerances and a smooth surface finish. This design for a 3D printed microscope stage uses plastic flexures, meaning its motion is free from friction and vibration. It achieves steps well below 100nm when driven with miniature stepper motors, and is stable to within a few microns over several days. This design aims to minimise both the amount of post-print assembly required, and the number of non-printed parts required - partly to make it as easy as possible to print, and partly to maximise stability; most of the microscope (including all the parts with flexures) prints as a single piece. The majority of the expense is in the Raspberry Pi and its camera module; the design requires only around 100g of plastic and a few nuts, bolts and other parts. The optics module (containing the camera and lens) can be easily swapped out or modified, for example to add epifluorescence or change the magnification. The location with OpenSCAD design files can be found here: https://github.com/rwb27/openflexure_microscope Associated Publication: http://dx.doi.org/10.1063/1.4941068 . Other projects that inspired this work: OpenLabTools microscope http://www.openlabtools.org/.