The Smithsonian characterizes the tunnel book by “a series of cut-paper panels placed one behind the other, creating the illusion of depth and perspective. Often, these are engineered like an accordion, with the two boards pulling apart and the illustrated panels lined up and viewed through a front peep-hole or viewer.” While these structures date back to the 18th century, book artists today continue to make use of the tunnel book in fascinating ways. Maria Pisano of Memory Press says, “A tunnel book is a fantastic 3D structure that allows the viewer to look within and discover a hidden world, which evolves in accumulated layers, bringing one back to days of wonder, discovery, and the creative self.”