1 millimeter | mm | one thousandth (10-3) of a meter | roughly the thickness of a credit card, a pencil tip, or a blade of grass |
100 micrometers | 10 thousandths (10-4) of a meter | roughly the thickness of a human hair (17-181 μm), or a piece of paper (70 to 180 μm) | |
10 micrometers | 100 thousandths (10-5) of a meter | roughly the thickness of a cotton fiber, or a human red blood cell | |
1 micrometer | µm | one millionth (10-6) of a meter | roughly the thickness of E. coli bacteria, or spider silk |
For the machinists out there, note that 1 thou is 25 micrometers.
This video contains a LOT of wisdom about how to do finishing on miniatures. The miniatures that we're having printed for us are usually made using a resin (SLA / stereolithography) 3D printer.