A CRT TV, or cathode ray tube television, is a type of television that was widely used before the invention of flat-screen televisions. It is essentially a vacuum tube that contains one or more electron guns and a fluorescent screen that is used for viewing images. The electron beams are accelerated and deflected onto the television screen to create the actual images, which can symbolize electrical waveforms in an oscilloscope, and pictures in television screens and computer monitors. CRT TVs have a specific look that is hard to describe, but it is unachievable via OLED or LCD. They have a boxy design, with a back angled down and away from the screen before squaring off, and the screen is convex, meaning that it curves outward, away from the frame. CRT TVs were popular until the mid-late 2000s when they were superseded by flat-panel display technologies such as LCD, plasma display, and OLED displays, which are cheaper to manufacture and run, as well as significantly lighter and less bulky. CRT TVs are difficult to recycle and contain toxins such as lead and mercury, which require special handling.