Pretty Good 400μm tall RepRapMicron Logo, 20μm Feature Size.

This one came out well. I've made a test square in gcode that gradually spirals down 2μm a side, and I reset the Z height every time I run it until I touch the surface, then back it out to correspond with the height of the first side of the square that touches. This needs to be done to a precision of 1μm, and because it's a fairly consistent and binary scratch/no scratch I'm pretty sure I'm getting 1μm accuracy on the Z height. The lines are wavey because the relatively blunt tip on the hypodermic is hitting surface imperfections and pushing around them, as you can see at the roughly 4 o'clock position on the outline:

This might get better with a finer tip as there is less material on the probe for potential collisions and a sharper cutting edge. I'll try that next. As you can see from the image, the smallest feature - the thin bottom curve on the μ - is a 20μm gap. This is approximately the pixel size of a good home MSLA printer. The line width is somewhat less than 10μm which is the best I've ever managed with a hypodermic needle tip.