Frenchman Louis Daguerre - alongside French inventor Nicephore Niepce - developed the first form of mass photography. His Daguerreotypes were photos on a metal plate, enclosed in a jewel case. Many people - usch as George eastman and Matthew Brady - got their start in this form of picture-making.
See more of them at the Library of Congreess site called American Memories. Please see Daguerreotypes.