Above: The earliest reliably dated photograph of people, taken by Louis Daguerre one spring morning in 1838.
Tech chat about the process here Scientists found these old photographs contain metallic nanoparticlesNicephore Niepce is now widely credited with taking the first still photograph in July of 1827, using a material that hardened when exposed to light to capture the image. But it took a full eight hours of exposure, and the image was temporary. Louis Daguerre built on Niepce's work, figuring out how to reduce exposure times and fix the images by immersing the photographic plates in a salt solution. Introduced in 1839, his "daguerreotypes" were all the rage for several decades—Abraham Lincoln and Emily Dickinson were among the luminaries whose portraits were captured this way, along with the transit of Venus and the horrors of the American Civil War