In 1833, Niepce died, and Daguerre invented, in 1838, on his own the daguerreotype, the first process including a development stage. A silver plate coated with a very thin silver iodide layer was exposed in a camera obscura, then exposed to mercury vapors that induced the apparition of the invisible latent image that had been formed during the exposure to light. This development was in fact such an amplification of the effect of light that the exposure time was hardly more than 30 minutes. Fixing was done by immersing the plate in sea salted water.