Transcript for The Dress That Broke the Internet: Explained
That darn dress. You know the one I'm talking about. It's been inescapable today. Dividing the world between those who see white and gold, those who see blue and black. Tonight we went in search of answers. When you can't believe your eyes what can you believe? Lama Hasan investigates. I swear white and gold. Reporter: White and gold, blue and black? What colors do you see? It's this picture of this dress posted by scottish singer date tin Mcneil that's launched more than a million tweets and counting. Blowing up the internet. No one immune from #dressgate. ? Reporter: Even the ever in-style Taylor swift weighing in on fashion's big debate tweeting, I'm confused and scared. Yes, it's obviously blue and black. Anna Kendrick tweeting, if that's not white and gold, the universe is falling apart. The company behind the divisive dress wearing the controversy well. Traffic up 2,000%. At this store in the UK, the dress sold out by mid-day. I have to ask you -- It's blue and black. Reporter: This morning the designer behind the dress showing its true colors once and for all. Blue and black. It's clear as day to me. But as you know people are saying that they see white and gold. Reporter: So what is it about this picture? Neuroscientist Pascal wallish say our brains interpret things differently. Like a game of telephone. Reporter: The image that reaches our brain sometimes different than what our eyes perceive. We need to move past this idea of correctness. The reality is richer than your perception. Reporter: The only thing we're perceiving, this is a must-have dress of the moment. For "Nightline," I'm lama Hasan in London. I don't know anymore. So what color does the dress look like to you? Head to our Facebook page and join the debate.
This transcript has been automatically generated and may not be 100% accurate.