In the last third of the 19th century, photography had the power to be enlisted as a tool of social reform. Jacob August Riis, a muckraking journalist, began to use photography in the 1880s to expose conditions in New York slums. Sociologist Lew Hine, two decades later, supported a campaign for child-labor laws with sympathetic portraits of young factory workers.
Photography also was applied within the same time frame to scientific inquiry. Cameras were attached to microscopes and telescopes and produced strange pictures from nature. Scientists and social reformers both profited from the continuous technical improvements in photography. Among the important innovations were the introduction of dry plates in the 1880s and flexible roll film in 1888.