In CRT displays, a beam of electrons is accelerated under high voltage and made to collide on a phosphor-coated screen. The particular phosphor elements that are hit by electrons are illuminated. In monochrome CRTs, each pixel is represented by a single phosphor element, while in colour CRTs, each pixel has three phosphors, each one capable of emitting red, green, and blue light. The electron beam constantly scans the screen, starting from the top left corner and ending at the bottom right corner, refreshing one row at a time.
Cathode Ray Tube technology is the predominant—though dated—technology, still powering most monitors. The high voltage needed to power up the display and the space the monitors occupy, in addition to the eye-strain caused by the flickering of the scanning electron beam, are the reasons for looking for alternatives. The ability to display at any resolution without loss of clarity puts them at an advantage over LCD screens.