Everybody's talking about loom bands, the most popular playground craze of all time (yes, even bigger than conkers – get with the programme!).
Kids try to out-do each other with their finger-woven rubber band creations; parents are driven bananas by finding loom bands clogging up vacuum cleaners and plugholes.
Celebrities like David Beckham and One Direction's Harry Styles love them.
And the Duchess of Cambridge's parents, Michael and Carole Middleton, have started selling glittery loom bands on their Party Pieces website.
As we all know (by now), loom bands are small, colourful rubber bands that can be linked together on a plastic Rainbow Loom (which has sold more than three million units worldwide!).
Children use the looms, or their own fingers, to weave coloured bands into items such as bracelets, necklaces and charms.
The multi-coloured bands sell for as little as £1.99 for 1,800. But how did they become so popular?
The Rainbow Loom was invented in 2011 by Cheong Choon Ng, a Malaysian-born former seatbelt technology developer from Michigan, who noticed his daughters weaving elastic bands over their fingers to make bracelets.
Ng tried it but his own fingers were too big, so he built himself a 'loom' - a technology known to the clothing trade since at least the 15th Century - using pins and a wooden slab. His daughters were impressed with the more intricate patterns this allowed.
Ng then developed a plastic version and set up a business manufacturing them, investing $10,000.
He got a toy shop to stock his product and, after it sold out within a few hours, other stores took an interest.
It spread from there and looms and bands can now be seen in schools and homes around the UK and US.
Richard Gottlieb, founder of consultants Global Toy Experts, said: "It wasn't driven by advertising or big companies.
"It's what I call the social network of the playground. It started out in a specific geographical location and just spread from there. You get these phenomena every few years."