Pareidolia is the phenemenon of seeing an image of something, from an otherwise completely random arrangement. For example seeing faces in clouds.
Here is an example of pareidolia in wood. You can see a dog's face, ears and front legs, which has been created unintentionally by the random arrangement of the grain. Incidentally, the Welsh for pareidoila is also pareidolia.
Some religious people think they've seen Jesus Christ !!!