I continue to find it amazing that something as “bulky” and macroscopic as a static magnetic or electric field is actually a manifestation of virtual photons.
So putting on your QFT spectacles, look closely at the space near the pole of a powerful magnet – virtual photons! Now look between the plates of a charged capacitor – virtual photons again!
But if it’s all virtual photons, how do we get the difference between a magnetic and electric field?
[This question needs the tag "magnetostatics" as well].