The project began with a book found in the attic of a family house: Ce que vaut une femme, a treatise on the moral and practical education of young girls, published in 1893 with the support of the ministry of public instruction. Its contents seemed at once instructive and comic.

The tone is set from the opening, written by its author Éline Roch, who had won a prize for it in 1893: what would become of our country the day a woman found herself turned away from her natural destination, the day a young girl could suppose that something else existed for her.

Elsa & Johanna answer it with the twelve hours of the day and of the night, made on an original idea of the publisher, with a text by Marie Robert, chief curator at the Musée d'Orsay.