Looking a bit closer at it, I would say that the bands you see on the feet and body seems like the "precision" of the system. These are around 4 pixels wide. The 20µm ruler is 84 pixels wide, giving us 20µm / 84pixels ≈ 0.25µm/pixels.
So the band is 4 pixels * 0.25µm/pixels = 1µm. (Assuming my premises are right)
That was about 2 years ago now. Very glad to see they made such great progress in the meantime (-: