It is known only as the dress, and it caused massive strife for families, friends and the internet on Thursday.
After much shouting in the office, some sleuthing, and wild pontificating, BuzzFeed News talked to the original poster, Caitlin McNeill.
McNeill, a member of the ceilidh (folk band) Canach, is from the Hebrides, islands off of Scotland. Last weekend, the band was asked to play for the wedding of her friends Grace and Keir Johnston on the island of Colonsay.
"I'm a friend of the dress," McNeill joked.
About a week before the wedding, the mother of the bride sent a photo to the couple of what she planned to wear. That's when the first disagreements began.
The bride and groom couldn't decide if the dress was blue and black or white and gold. So they posted the photo on Facebook.
"We all went crazy trying to figure out why some people were seeing white and gold, and others saw blue and black," McNeill said.
Of course, in person, McNeill said it was obviously blue and black. But the photo still didn't make any sense to anyone.
"I showed my band ... who were playing at the wedding with me, and we all fell out trying to decide what the problem was," she said. "We almost didn't make it on stage because we were so caught up discussing this dress."
They made their performance, though, and the wedding was lovely, McNeill said. She then forgot about the strangeness of the photo until Thursday, when she posted it to her Tumblr.
"Then it went absolutely mental," she said. "Some friends tweeted it, and within the hour I had tens of thousands of notes, tweets, messages."