[Namahanna]

Carl Zeiss makes some amazing optics to allow it all to happen https://www.asianometry.com/p/how-carl-zeiss-crafted-a-house...

To quote:

To make these EUV mirrors, each 2 to 4 nanometer layer of molybdenum and silicon has to be deposited one by one. Fifty times, without fatal defects.

After that, each mirror has to be painstakingly polished. The acceptable surface deviation metric is 50 picometers, or 50 trillionths of a meter. That is a staggering number.

To put that into perspective. 50 picometers on a mirror that is 450 millimeters wide. If that 450 millimeter mirror was blown up to the size of the United States, 4,500 kilometers or 2,800 miles wide, then 50 picometers would be just 0.5 mm tall.

[nealabq]

Altho there's a couple ways to define an atomic radius, molybdenum's and silicon's empirically measured covalent atomic radii are 145 and 110 picometers respectively [1]. So 50pm is a very small bump indeed.

[1] https://en.wikipedia.org/wiki/Atomic_radius