Users post photographs, share comments and links, and interact on community pages that have become huge forums based on themes as diverse as recipe-sharing and Michael Jackson.

A set of unseen Michael Jackson pictures is reportedly set to be sold at auction later this year, and miraculously, Joe Jackson doesn't even have a hand in it!

For instance, one cell in the temporal lobe might respond to seeing a picture of Marilyn Monroe, while another might respond to Michael Jackson.