ACEO stands for Art, Cards, Editions and Originals. They are miniature pieces of art that strictly measure 2.5" by 3.5", and can be any media, including photography. Some of my ACEO's are miniatures of my larger photos and some are only available as ACEO's. All come matted with either black or white/off-white mats, and ready to put into any 4"x6" frame.