Everyone's eys are wired differently.

http://www.msnbc.msn.com/id/10239783/

"The first images ever made of retinas in living people reveal surprising variation from one person to the next. Yet somehow our perceptions don't vary as might be expected."

This is cool. Back in high school a concept was brought up about how people might precieve the world differently to other people, based on what they see. Sure they might recognize the same color, but to what effect. Maybe someone see the world in more of a shade of red, but is used to it, and this is normal to them, while, someone else would see in more of a green color. From day one we learn what is normal, but how do we know what someone else sees isn't slight off in color or hue.