Cyanotypes are one of the oldest photographic printing processes in the history of photography. The distinctive feature of the print is its shade of cyan blue, which results from its exposure to ultraviolet light. When the blueprint emerged, cyanotypes were traditionally used for reproducing the technical drawings of architects and engineers until the arrival of photocopy machines. Cyanotypes were first introduced by the astronomer, scientist, and botanist John Herschel in 1842. Although Herschel had discovered the process, it was the botanist and photographer Anna Atkins who first used the cyanotype to create a photographic album of algae specimens in 1843.