Fermions

Fermions are particles which obey the laws known as Fermi-Dirac statistics. They include electrons, muons, protons, neutrons and most of the particles we meet on Earth.

They have the property that no two particles with the same energy can occupy the same space. This means that space fills up with particles. This is the reason why electrons create shells around atoms, why stars do not collapse into black holes, and why you and I do not shrink into specks of matter.

This behavior is in contrast to that of bosons.