It's the debate of the year so far and it's driving everyone a bit crazy. Have your mates all fallen out yet?
The question is all about whether you see #TheDress as blue and black (#blueandblack) or white and gold (#whiteandgold).
Sounds like it can't be hard to decide. That's where you'd be wrong. Oh so wrong.
The global, yes global, debate all kicked off when Scottish singer Caitlin McNeill posted a picture of a dress on her Tumblr blog.
She asked her followers: "Guys please help me - is this dress white and gold, or blue and black? Me and my friends can't agree and we are freaking... out."
Caitlin told Newsbeat that it all started when her friend's mum wore the dress at a wedding.
"Two of my very good friends were getting married and they has asked me to put together a band to come and play at the wedding," she says.
"A week beforehand the bride had been sent a picture of the dress she was going to wear and when the bride showed her fiance, they disagreed about what colour it was. She was like, 'It's white and gold' and he said, 'It's blue and black'.
"So they posted it on Facebook to try and see what their friends were saying but that caused carnage on Facebook.
"We forgot about it until we saw it at the wedding which the mother of the bride was wearing and it was obviously blue and black."
There are lots of videos, like this below, trying to work out just what is going on with our eyes - and the science of colour.
A LOT of people are still debating the colour of that snapshot.
Various US news outlets have written stories about how the human eyes see different colours and why some people see blue and black while others see gold and white.
And then the analysis (LOTS OF IT) and the memes ( the memes!) started...
It's all great news for the makers of the £50 dress.
A quick check online shows Roman Women's Lace Detail Bodycon Dress is available in Royal Blue - so blue then...
And the company says it's looking into doing a gold and white version of the dress.
A spokesman told Newsbeat: "We're looking into getting it through the approval stages.
"We want to do it but it depends on the speed. We're trying to get it done as soon as possible.
"We are in contact with the suppliers to establish if we can get it manufactured in white and gold."