Quark

The quark is one of the two basic constituents of matter (see lepton). They make up hadrons, which are simply composite particles made of multiple quarks. Examples include various mesons (quark-antiquark pairings), baryons (made up of three quarks), and exotic states containing yet more quarks/antiquarks.

Size
Quarks are smaller than protons and neutrons; indeed, there are three quarks in each of these subatomic particles. As far as early 21st century scientists know, quarks together with leptons are truly fundamental and cannot be broken down further. They take their name from an invented word in a passage of James Joyce's stream-of-consciousness novel Finnegan's Wake.

Flavours
Quarks come in six delicious "flavours": up, down, charm, strange, top, and bottom.(Note: Yes, those are the real flavors.) Oddly enough, they do not come in mint, vanilla, chocolate, raspberry, strawberry, or any other normal flavors. Up, charm, and top quarks have a charge of +2/3, while down, strange, and bottom quarks have a charge of -1/3.

Fittingly, a proton consists of two "up" quarks and one "down" quark. Second and third generation quarks are unstable and will spontaneously decay into first-generation quarks in a few yoctoseconds or less, although hadrons composed of such quarks tend to last somewhat longer.

And scientists think the Higgs boson may be just what is needed to give quarks mass.

Trivia
Contrary to the snicker you will inevitably hear whenever you utter "quark," they do actually exist. At least one can be found serving drinks on Deep Space 9. They might be pronounced qu-ARK or perhaps qu-ORK, no one seems to agree.