A pinhole camera is an extremely simple type of camera. Simply put, a pinhole camera is a light-proof box with a small hole in it. Light from a scene passes through the aperture (small hole) and projects an inverted image on the opposite side of the box. When you put film inside the box, it will capture that image and you can develop it. It is simple to make, and you can find most materials in your house. The camera is also used best on sunny days.
To learn how to build go here: http://www.instructables.com/id/How-To-Make-A-Pinhole-Camera/
This relates to engineering because it took lots of research to build a functional camera out of such simple materials. The film also needed to be developed to correctly capture the image. This camera was made with many different engineering processes.
