Subseries is comprised of Cornell's files on various subjects, including topics of interest to him, themes, "explorations," art and publishing projects, and exhibitions. Some files are organized according to format, such as clippings, notes and writings, and stamps. Files typically consist of material that Cornell used in creating particular boxes, collages, and other works (design layouts and exhibition announcements, among others), and from which he drew ideas and inspiration for projects. Material typically includes magazine and newspaper clippings, cutouts, notes, writings, book and typed excerpts, stats, prints, postcards, art reproductions, and other printed material.

Subject source files range from slender files containing only clippings and cutouts of a particular subject (such as Butterflies, Food, and Statues) to files of assorted printed material seemingly related to some sort of titled, but not easily identifiable, project (such as "Animals in the News," "Earth Before the Flood" Box, and "La Malaga") to voluminous files relating to a particular topic, which Cornell explored in depth, or to an on-going project, which may or may not have resulted in a finished product (such as "Celestial Theater" and "GC 44"). Some files are more comprehensive than others; some files relate directly, and others only indirectly, to particular projects; and some files are so general and/or incomplete that it is not entirely clear how they relate to Cornell's projects or interests.

Certain subject source files relate to Cornell's "explorations" on such diverse topics as astronomy, ballet, literature, and music. Ones on astronomy include "Cassiopeia" (sparked by his musings on the constellation and his preoccupation with a young waitress) and "Celestial Theater" (an unfinished project on sky-gazing). Ones on ballet and literature include "Portrait of Ondine (Cerrito)" and the Bibliomania projects, respectively. And ones on music include "The Caliph of Bagdad" (sparked by hearing the opera by Francois-Andrien Boieldieu and leading to the creation of one or more Cockatoo boxes), "Famagouste" (inspired by the opera, "La Pisanella" by Ildebrando Pizzetti), and "Rossiniana" (involving a proposed "feuilleton-project" on the composer, Rossini).

Other subject source files relate to particular "explorations" based on Cornell's personal experiences. Most notable among these is "GC 44," which stemmed from events during the period when he worked at the Garden Centre nursery in Flushing. The extensive "GC 44" files document the core experiences of this "exploration," which included visits to "The Old Farm" (Lawrence Homestead), a dream of "the little dancer," many trips to the "house on the hill" (where Cornell gathered dried grasses which were used in his Habitat boxes), and a particular sighting of a delivery truck "with its enseigne of the fish and smoking meats" which inspired "The Floral Still-Life" musings. Also documented are Cornell's overriding concerns to recapture and recreate what was for him "one of the high tides of inspiration" and to share the experience with others. Though he exchanged ideas and shared some of this material with others ( See letter from Donald Windham to Betty Cornell Benton in Series 10), the project, as he imagined it, was never completed.

Some subject source files relate to particular art projects and stem from Cornell's work researching, planning, and/or creating certain box constructions, box series, and collages. While by no means comprehensive or complete, files on art projects variously document the origin of certain box series (such as the Aviary and Juan Gris series) and/or stages in the development of particular boxes and collages (such as the "Nostalgia of the Sea" box, and the Rabbit and "Tina" collages). Files on art projects also suggest the way in which Cornell's preoccupations influenced his art work, as in the box, "The Bird with the Shoe-Button Eyes," which stemmed from his preoccupations with literature in general and with the French author, Gerard de Nerval, in particular and which he seems to have conceived as a means to bring the rather obscure author to the attention of a wider audience.

Certain subject source files relate to particular publishing projects and stem from Cornell's work designing covers and illustrations, writing articles, and planning entire issues for various commercial and avant-garde periodicals ( See Subseries 4.1 for his work on self-publications). Notable publishing projects documented, in part, here include "The Crystal Cage [portrait of Berenice]," and various pieces for Dance Index, including ones on "blackface ballerinas," children and ballet, and dancing animals, as well as the thematic issue, "Clowns, Elephants, and Ballerinas" (1946).

Subject source files on exhibitions stem primarily from Cornell's work on catalogues for the "Objects by Joseph Cornell" exhibition at the Copley Gallery (September 1948), the "Night Voyage" exhibition at the Egan Gallery (February 10-March 28, 1953), and the "Romantic Museum at the Hugo Gallery: Portraits of Women" exhibition (December 1946), and they document, to a certain extent, his involvement in the presentation, exhibition, and sale of his art work.

It is unlikely that Cornell maintained these files in alphabetical order. Betty Cornell Benton's correspondence indicates that she organized some of his papers ( See Series 10), so it seems likely that this order was imposed by her. At this point, it is difficult to surmise what, if any, Cornell's original organization may have been. Therefore, files have been left in alphabetical order.