Four-jet event created by quarks & gluons in the SLD detector at SLAC, the Stanford Linear Acceler- ator Center, California. In the computer display, the detector is shown in cross-section in pale and dark blue and red. An electron & positron, accel- erated to high energy in SLAC's collider, have annihilated at centre to produce a quark and antiquark, which in turn radiate two gluons. These four particles are too short-lived to be seen, but reveal themselves when they in turn create the four jets (green tracks and coloured blocks). The gluon belongs to the family of elementary particles called gauge bosons and is the carrier of the strong nuclear force.