Heliography is an early photographic process that captures images using sunlight. Developed in the 1820s by Joseph Nicéphore Niépce, it involves placing a light-sensitive material, such as bitumen of Judea, on a metal plate. When exposed to sunlight, the material hardens in proportion to the light it receives, allowing for the creation of a permanent image after a long exposure time. This technique was one of the first methods to produce a photograph, paving the way for modern photography. Heliography laid the groundwork for subsequent developments in the field, influencing later processes like daguerreotype and calotype.