Flow of electrons generated in a cathode ray tube (CRT) by the electron gun and aimed at the back of the screen where the electrons excite phosphors causing them to glow various colors. The electron beam is similar to a brush used to paint a picture on canvas. The brush is dipped into the colors of paint and used to create the image. An electron beam “paints” an image on an array of phosphors that glow when stimulated making the phosphors similar to the paint and the electron beam similar to the brush. n electron beam is aimed or guided by a magnetic “yoke” in the picture tube. The beam passes through a shadow mask on its way to hitting the phosphors (the shadow mask has many holes allowing the electron beam to pass through to only one group of phosphors and not hit its neighbors unintentionally). The phosphors, excited by the electron beam, glow red, green or blue. Three phosphors form one pixel or picture element, their colors mixing to form any color in the rainbow.