Pierre Jahan is one of the artists who experimented with photography without a camera, along with Moholy-Nagy, Man Ray and Christian Schad. The photogram - or rayogram in Man Ray's term - consists of superimposing an object between photosensitive paper and a light source, in order to fix the image afterwards. This process produces negative silhouettes on the final photograph. Despite its use in the first half of the 20th century, the technique goes back a long way, having already been experimented with in the 19th century in the context of scientific illustration, particularly botany. Jahan pushed the technique in his own way, using it on photographic negatives to obtain unusual superimpositions of images.

Unlike Man Ray, Jahan returned to the scientific origins of the medium of the photogram: copies of grasses and other plants superimposed on photographs.