When you thermally excite an electron to a higher energy level, it quicky comes back to its ground state by realeasing its energy in the form of a photon(s). We all, I assume, accept this fact. But does it make sense? How does the electron do that? I thought that the electron was an indivisible particle without any volume. Then how can it emit a photon? Is this something that is left unexplained by physicists?