Wikipedia**
Gamma radiation, also known as gamma rays (denoted as γ), is electromagnetic radiation of high frequency (very short wavelength). They are produced by sub-atomic particle interactions such as electron-positron annihilation, ...
so the electron-positron annihilation produces photons?
based on this picture
if light is made up of little tiny massless particles called photons
what are radio waves made of?
what are microwaves made of?
what are infrared waves made of?
what are ultraviolet waves made of?
what are x-ray waves made of?
gamma rays are made of electrons and...