https://www.wired.com/story/build-your-own-pinhole-videocam/

The simplest way to project an image onto a screen is with a pinhole. What the heck is a pinhole? It's a hole so tiny it has to be made with a pin. See, science isn’t that hard.

People have been building image viewers with this trick for hundreds of years; it was originally known as a camera obscura, which means “dark chamber.” The idea was, you get some people in a dark room with only a tiny hole open to the outside. It seems magical, but the light from that hole would project an image of the outside world onto a wall in the room.