Smashing Pictures

In the first image, the production of three jets (or isolated groupings) of particles indicates the discovery of the gluon. Two jets are the remnants of quarks, and one is from a gluon. As the second image indicates, modern detectors can see gluons by the production of three jets. The height of the boxes indicates the amount of energy deposited in the detector, and the colors indicate how far into the detector the energy was deposited.