The subpixels in an LCD screen use liquid crystal molecules that act as light pathways and also as dimmer switches to let the backlight through, partially through or not at all to reach red, green and blue filters. For more on the red, green and blue concept, see RGB. When unenergized, the liquid crystals start out looking like twisted ladders because they orient themselves to microscopic grooves, called "rubbings," in top and bottom glass panels, and the rubbings are at right angles to each other. When energized by electrodes at the top and bottom, they re-orient themselves away from the orientation of the front polarizer panel, and the more they twist away, the less light reaches the color filters, which create the red, green and blue lights. Up to 240 Changes Per Second In an LCD HDTV set, the subpixels can change their state up to 60 times per second. In a 3D TV or computer monitor, it can be up to 120 times per second, and in a 240 Hz TV, up to 240 times per second. See LCD and LCD example.