How did Joseph Nicephore Niece invent the camera?

The world's earliest known image created exclusively by the action of light was Joseph-Nicéphore Niepce's 1827 photograph of a tree, barn and building. Known as "The View from the Window at La Gras", the image was captured using a Camera Obscura, a device generally credited to Ibn al-Haytham (965-1039 AD). To create the photograph, Niepce focused an inverted image onto a light-sensitized pewter plate coated with a type of asphalt known as Bitumen of Judea. According to some estimates, this photograph required something between several hours and several days to expose.