The quark is one of the two basic constituents of matter (see lepton).
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. 
Quarks come in six delicious "flavours": up, down, charm, strange, top, and bottom. Oddly enough, they do not come in mint, vanilla, chocolate, raspberry, strawberry, quark cheese 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. And scientists think the Higgs boson may be just what is needed to give quarks mass.
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, noone seems to agree.
- Quarks and Leptons
- Quarks dancing to polka music. You know you want to.
- For those who grew up in the 90s, Captain Qwark!