Some people will swear up and down that the dress is blue and black. Others insist, without any doubt, that it's white and gold.
But then why do so many people see it so differently in the photo?
Visual scientists can mostly explain what's going on here: We interpret the color of objects based on how we interpret the light around those objects. Different people are interpreting the ambiguous lighting in the dress photo in different ways, so their brains are essentially tricking them into seeing the dress as different colors.