Photography has come a long way in its relatively short period of time. From the 5th century Camera Oscura to the Contemporary DLSR ( Digital Single-Lens Reflex Camera).
Even if the concept of photography has been around since about the 5th century B.C. , it wasn’t until an Iraqi scientist developed something called the camera obscura in the 11th century that the art was born.
The first camera obscura used a pinhole in a tent to project an image from outside the tent into the darkened area. However the camera simply projected images onto another surface upside down, so that they could be traced to create accurate drawings.
It wasn’t until the 17th century that the camera obscura became small enough to be portable. Basic lenses to focus the light were also introduced around this time.
Nièpce and Daguerre
Photography, as we know it today, began when Nicéphore Nièpce started experimenting with other light-sensitive substances and invented a process named heliography. In 1826, he shot the earliest surviving photograph. It represented a view from a window at his hometown in Burgundy, captured on a pewter plate coated in bitumen diluted in lavender oil. The exposure time was probably several days.
image source: https://en.wikipedia.org/wiki/History_of_photography
A few years later, Nièpce went into partnership with Louis Daguerre, and together they improved the heliograph process, substituting a more light-sensitive resin and improving post-exposure treatment.
After Nièpce died in 1833, Daguerre developed a technique in which a silver-coated copper plate fumed with iodine vapour formed silver iodide when exposed to light in the camera.
He made a major breakthrough when he found that a “latent” image obtained from a brief exposure could be further developed and made visible by exposing it to mercury fumes: in this way exposure times (which previously were several hours) could be reduced to a few minutes.
info source: https://www.britannica.com/technology/photography