The width of a Silicon atom is about .2 nanometers (nm). A 4 nm chip means 20 atoms thick. Chip making is basically at the bottom by this point.
They be tiny. ASML makes the highest-res ultraviolet lithography equipment in use, it was interesting to see that in the video.
[snip] A human hair is 100,000 nanometers wide. As you can imagine, then, the human eye can’t see anything that’s 1/100,000th of the size. It’s not even visible to most microscopes, instead requiring atomic force microscopes. A strand of human DNA is 2.5 nanometers, which makes it incredibly small, but still larger than some of the transistors currently in development. Atoms and quarks are both smaller than a nanometer. While they vary in size, atoms can be anywhere from .1 to .5 nanometers in diameter... Silicon has an atomic radius of .117 nanometers, which is smaller than Gallium’s .122. Even though the differences in atomic size can be small between two elements, these changes can be significant when discussing nanotechnology. [/snip]
https://www.waferworld.com/post/how-small-can-transistors-get