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In the mid-19th century, Sir John Herschel invented the cyanotype, an intricate photographic process that uses iron compounds to create prints with a lustrous blue hue. His close friend Anna Atkins, an amateur botanist who took particular interest in scientific illustration and taxonomy, decided to use the new technique to document algae from her extensive seaweed collection, resulting in ethereal, highly detailed illustrations rendered in wispy shades of white set against a radiant cyan background, also known as Prussian Blue. She then published her works in
Photographs of British Algae: Cyanotype Impressions, widely considered to be the first book illustrated with photographic images. Cyanotypes became a simple, low-cost process to produce copies of drawings, commonly referred to as blueprints.