The smallest packet of electromagnetic energy that can be absorbed or emitted is a proton.

A photon is the smallest packet of electromagnetic energy that can be absorbed or emitted. Photons are the basic unit of electromagnetic energy, and are massless particles that can travel with the speed of light. Photons are responsible for the electromagnetic force, which holds together atoms and molecules. They can also transfer energy between particles and waves, providing the energy needed to create light, visible and non-visible radiation, and even to carry information such as cellular and Wi-Fi signals. This is supported by the fact that photons can be easily absorbed by other particles, which is why they are often used in imaging technology, like radiography and MRIs, and to generate electricity through solar cells.