The Karoussos Archive holds the entire visual material of the late fresco painters Dionysius and Yannis Karoussos, who represented two major avant-garde art periods in Orthodox Ecclesiastical art:
i. The Nazarene (pre-Raphaelite) movement, which was a reaction to Neoclassicism and the academy system's conventional art education, and
ii. The renaissance of contemporary meta-Byzantine art, distinguished by an enriched post-Paleologan personality.

Over 200 original worksheets (anthivola) from major mural paintings in Orthodox churches, including the Athens Cathedral, St. Panteleimon in Athens, St. Andrew in Patras, and many others, are preserved in the Archive.
Tens of thousands of photographs and slides were captured during the construction process from scaffolding levels, depicting details found as high as 43 meters above ground level.
These images are especially valuable because they contain details of frescoes that would otherwise be impossible to study due to the height and scale of the churches. Furthermore, they illuminate the layers of the painting work process in general.

Dionysis Karoussos started the collection in the early 1900s, and it contains a large number of late nineteenth-century gravures and lithographs, as well as rare anthivola from the painter's final Nazarene period.
After the mid-twentieth century, the Collection grew to include Yannis Karoussos's unique repository of post-anthivola (large worksheets on rice paper, which were used as blueprints for monumental, mural paintings in churches). Many of these worksheets are redrawn, including notes, in order to solve architectural problems such as distortion and perspective.

Many of these worksheets include the architectural plan and iconographic circle of the churches where the mural paintings are placed. This section of the archive is significant because it illuminates the long history of the modern construction of twentieth-century churches, where the use of concrete in the dome construction was particularly innovative.
Both painters' libraries round out the Archive's collection. They include some rare publications as sources for their artwork.