This theoretical particle, considered to be the fundamental unit of matter, was named by Murray Gell-Mann (1929–), an American theoretical physicist who was awarded the 1969 Nobel Prize in Physics. Its name was initially a playful tag that Gell-Mann invented, sounding something like “kwork.” Later, Gell-Mann came across the line “Three quarks for Master Marks” in James Joyce’s (1882–1941) Finnegan’s Wake, and the tag became known as a quark. There are six kinds or “flavors” (up, down, strange, charm, bottom, and top) of quarks, and each “flavor” has three varieties or “colors” (red, blue, and green). All 18 types have different electric charges (a basic characteristic of all elementary particles). Three quarks form a proton (having one unit of positive electric charge) or a neutron (zero charge), and two quarks (a quark and an antiquark) form a meson. Like all known particles, a quark has its antimatter opposite, known as an antiquark (having the same mass but opposite charge).