So from what I seem to understand up until now, Maxwell's equations usually work while assuming that the fields are continuous and smooth instead of the actual complexity at the atomic scale. However, as we move more and more towards the microscopic realm, a point comes when we cannot ignore this miniscule field variations and we need to change our approach. What exactly is that length scale? Is there a specific term for it? What changes do we need to apply to the macroscopic equations to make them work at this regime? I apologise if some of the questions in the thread don't make any sense, I'm rather new to Electrodynamics, especially at the microscopic level and I was wondering about the length scale where things will get troublesome. Thanks.