Often it is claimed "we have drawn a line x nm wide" or "a y nm hole was achieved" but the hardest thing is to print two such small features side by side, and only two.

Like two small contact holes or two closely spaced transistor gates. The distance between the two features can be harder than the feature size itself. It can be strongly disturbed by defocus and other effects. The distance between two contact holes is especially disturbed by shot noise and secondary electron proximity effects. The distance between two lines is especially sensitive to roughness for the same reasons.

So 'reality' breaks down then?
Alice in the wonderland :) as we wander down to those smallest definitions of our 'reality' and the way we do it is by 'radiation'. That supreme 'substance' that doesn't seem to want to decide whether it's a particle or a wave.