Cathode ray tube (CRT) displays were commonly used but are being replaced by newer technologies. CRTs use electron guns and phosphors to display images but have disadvantages like large size, weight, and power consumption. LCD displays use liquid crystals and do not emit light, instead blocking light to produce images. They are thinner and more energy efficient than CRTs but have limited viewing angles. Plasma displays utilize cells of charged gases to produce bright, large displays but also consume more power than LCDs. Newer technologies continue to improve on displays, with OLED providing thinner, more efficient self-emissive panels, LED backlights enhancing LCDs, and higher resolution 4K becoming more common.