A subatomic scale refers to objects smaller than an atom, for example, a scale at which the constituent atomic nucleus and electrons are apparent. The phrase is also sometimes used to refer to the still smaller subnuclear scale, the scale at which the constituents of the protons and neutrons of the atomic nucleus become apparent, namely the quarks and leptons. (The term "subnuclear" also is used in biology to refer to the constituents of the cell nucleus.)