it cold, is it white? take a look at this dress, a long, hard look, folks. >> yeah, this dress has sparked an important debate on the internet, not to mention boosting sales for the british website selling the dress. want to bring in our senior medical correspondent, elizabeth cohen. this is an important discussion about science. what color is the dress and how is there a debate over what people are actually seeing here? >> it's so weird, it reminds me of when i go to get burritos and i ask for extra cilantro because i love cilantro. but other people, my friend who i go with says, it tastes like soap, how could you eat that? this is the vision version of the cilantro debate. it's just genetically how you're wired. there are these cones on the back of our retinas. 99% of the time, we see the same