Animation cels are the pieces containing the full color images of cartoon characters which actually went before the cameras during the making of an animated film. Based on an animator's original pencil sketch, each cel is a transparent sheet which, after inking and painting, can be placed over an animation background for filming. Each production cel presents the character in a slightly different position or expression, necessitating a one of a kind, original piece of art for each movement. When filmed in sequence and projected, the cels create the illusion of life.

Some recent anime shows in Japan, such as "Love Hina", now use computer graphics in place of animation cels. As more and more shows switch to computer graphics, animation cels will become more scarce, and hence, more valuable.