Standard Model of elementary particles.
1 GeV/c² = 1.783x10^-27kg. 1 MeV/c² = 1.783x10^-30kg.

In physics, an elementary particle or fundamental particle is a particle that is not made of other particles.

An elementary particle can be one of two groups: a fermion or a boson. Fermions are the building blocks of matter and have mass, while bosons behave as force carriers for relations between fermion and some of them have no mass. The Standard Model is the most accepted way to explain how particles behave, and the forces that affect them. According to this model, the elementary particles are further grouped into quarks, leptons, and gauge bosons, with the Higgs boson having a special status as a non-gauge boson.