The photon : an elementary wave
a fundamental wave: A photon is a microscopic electromagnetic wave, caused by oscillations in the electric and magnetic fields through space and time. A wave, in the classical sense of the term, consists of infinite oscillations and can never be localised. The number of oscillations in the photons emitted by atoms and nuclei is not infinite, thanks to a small uncertainty in their energy values. The shorter the wavelength of the photons, the denser the wave is in space. When the wavelength is as short as is the case with gamma rays, then the waves become dense enough to resemble particles.
IN2P3