ACEO stands for Art Cards, Editions, and Originals; they are miniature, original artworks that measure precisely 2.5 x 3.5 inches (64 x 89 mm). ACEOs are created to be bought and sold, and can be made with a wide variety of materials such as watercolor, oil, collage, or acrylic. These small, collectible pieces are popular for both collectors and artists as a way to buy and sell original art affordably.