Plasma TV's create a picture from a gas (plasma) filled with xenon and neon atoms and millions of electrically charged atoms and electrons, that collide when you turn the power on. The energy the collision releases increases the energy level in the plasma and the neon and xenon release photons of light (similar to the way neon lights work). Plasma TVs offer large viewing areas (up to 50 inches) but are very thin. While they offer excellent picture quality, they are quite expensive and are fast becoming the popular choice for HDTV.
See also plasma display.