Liquid Crystal Displays or LCDs use a grid of liquid crystal filled cells, each representing a pixel. In color displays, each pixel is comprised of three sub-pixels with red, green, and blue color filters. When a varying voltage is applied to each cell the crystals can show colors of varying intensities.

LCD screens do not produce their own light; therefore efficient LED (Light Emitting Diode) or florescent back-lights are needed.

• Active Matrix : An LCD technology a thin-film transistor (TFT) for every pixel on the screen. This enables precise response to pixel changes and offers a better contrast ratio to the screen. If a pixel transistor fails then the pixel will be rendered into a permanent stuck state, also known as a bad pixel. In some cases a bad pixel can be repaired by applying light pressure to the affected region or by running a screen saver that flashes high contrast graphics, in attempt to force the transistor to work again. Almost all modern LCD displays use Active Matrix technology.

• Passive Matrix : An old LCD technology that had one row and column of transistors rather than a transistor for every pixel as in Active Matrix displays. Passive Matrix screens were plagued by poor response time, generally blurrier graphics and a worse contrast ratio. If a pixel went bad on one of these displays a whole vertical column or horizontal row of bad/stuck pixels would appear. Since LCD panels have dramatically dropped in price its now feasible to implement the superior Active Matrix technology, even in bargain display panels.