Who knew algae could take on such ethereal, beautiful forms?

These 19th-century photos of algae hold up today as art, but they're also a window into the development of photography. They're part of a new digital archive the New York Public Library put online.

The images were made by English amateur botanist and photographer Anna Atkins (1799-1871), who may have been the first woman to create a photograph, according to the library. Atkins is also the author of Photographs of British Algae: Cyanotype Impressions, which is thought to be the first book illustrated entirely by photography.

To photograph the algae, Atkins used the cyanotype process that had been invented by her friend Sir John Herschel in 1842. A version