Webm? Kinda sus.

Tektronix had originally developed their storage tubes in the late 1950s as a way to store images on oscilloscope displays for study, although the same system had already been used in radar displays. The basic concept used a conventional CRT layout, but with two sets of electron guns. One, the flood gun, provided a constant flow of low-energy electrons covering the entire screen, causing it to glow faintly. The second source, the write gun, resembled the normal gun of a black and white TV, and its beam was moved about on the display surface in the conventional fashion by using electromagnetic coils.

However, this write gun was set to a higher than normal energy. When its beam struck the screen, it caused an effect known as photoemission that expelled electrons from the light-emitting phosphors and towards the front of the display, where they were drained away by a thin transparent electrode. The "written" patch of the phosphor now contained fewer electrons than normal, giving it a positive charge relative to its surroundings. This caused more of the electrons from the flood gun to be continuously attracted to that spot, which kept it emitting an intermediate intensity of light. Thus, a complex image could be "stored" in the same light-emitting phosphors which made the image visible to the user.

Don't worry about where I got it from.