Originally, the JumboTron was not an LED display (light-emitting diode display), since blue LEDs were unavailable at the time, and the only green LEDs available were of the traditional yellow-green variety, which were unsuitable for an RGB display. Each display consisted of multiple modules composed of 16 or more small flood-beam CRTs (cathode ray tubes), each of which included from 2 to 16 pixels composed of red, green, and blue phosphors. Sony displayed one of the earliest versions at the Expo '85 World's Fair in Tsukuba.