Let me try ben.Photons are products of excited (heated) atomic matter. The wave frequency (beats or waves per second) of the photons of white light are so high that it can reach 400 to 790,000,000,000,000 waves per second! (Tera-hertz frequency)
With such erratic motions it would be impossible for a photon to become a solid or permanent piece of any molecular or atomic configuration. If in a laboratory, one attempted to forcibly make a photon join in with say a particle of Earth dirt, the photon would just bounce away unable to be joined with the solid matter. It may be the case because the photon cannot be contained in a magnetic field.
Ultimately however, like electricity, we can only know what a photon DOES and not what constructs it, it is I believe, what I'm going to term a "base unit" of the Universe.
(I am a "layman"... have I come close on my statements? )
The motion of the photons, erratic as they are, can still make up spatial freedom inside an atom. If we can deal with infinitesimal units of strings in string theory, just shows how much space a fundamental particle can take up. Even in the confinements of a particle with rest mass.