I've never found a good link, and I'm not certain that I know best, but I can try to explain it to you.

First: an understanding of the Pauli exclusion principle. Often people ask "Why can't there be 3 electrons in that orbital, there's plenty of space?" The thing is that the electrons are completely¹ defined by just 4 numbers: spin (±½), shell (positive integer), subshell (integer from 0 to shell-1) and magnetic (integer form -subshell to +subshell). Why there can't be more than 2 electrons in the 1st shell is that you can chose spin from (±½), shell is 1, subshell has to be 0, magnetic has to be 0. Its like asking "Why can't there be 3 integers between 0 and 3, there's plenty of space?" and the answer is that whatever integer you come up with will be one of the 2 already known (1, 2).

Similarly, as I understand it, the fundamental laws of physics don't distinguish between "things" closer than 1 Planck length apart. That doesn't necessarily mean that the universe operates on a 1 Planck length grid, just that any two "things" separated by less than a Planck length are indistinguishable from one new "thing" with different properties.

I'm fairly confident in the PEP description, the Planck length one I'm less 100% sure about, but its how I understand it at least.

¹assuming a universe comprised of only a single hydrogen atom, otherwise the states of everything else in the universe can perterb the state functions and things can get messy, but usually not enough to merge shells.