The branch of physics known as quantum chromodynamics studies what aspect of the subatomic world?

Quantum Chromodynamics or QCD, is the study of the interactions between quarks, named after a line in James Joyce's "Finnegans Wake," quarks are now known to come in six "flavors." The up quark and the down quark form the first generation of quarks and are the building blocks of every day matter. The charm and the strange quarks are the second generation of quarks and are found in certain types of particles known as mesons. The top and bottom quarks are the final generation of quarks.

Gluons are the exchange particles for the strong force and act between quarks. This interaction is also known as the strong nuclear force and is responsible for holding the nuclei of matter together.

An interesting fact about the strong force is that the force gets stronger as the distance between quarks increases which prevents us from ever isolating an individual quark from either generation one or two.