The Cyanotype process is an old photographic process that produces a Prussian blue print due the reaction of iron sats to light sensitivity.
During the process, no kind of ink is used to obtain the image, but it is the light that, when coming into contact with the sensitized paper through a negative, forms the image by a chemical reaction.
The cyanotype process was discovered in 1842 by the astronomer John Herschel, but it was the botanic Anna Atkins who used the technique in 1843 to edit and self-publish an illustrated book series about algae species.
She needed to reproduce the details of the different species. The cyanotype process allowed her to achieve that by creating the photograms from the plants itself, thus illustrating the scientific species in the most objective way, greatly surpassing the expectation for that period in time. Her work went beyond the scientific field, adding value to the arts and aesthetic disciplines.
Her book British Algae: Cyanotype Impressions it's consider the first photographic book and, Anna Atkins, the first woman photographer.