You might be wondering what an Ice Bucket Challenge is. Or why YouTube has suddenly become the place to see Chris Pratt, Robert Downie Jr and co drenched in water.
Well, forget the no-make-up selfie, when it comes to innovative ways of raising awareness and money for charity, nowadays it's all about buckets of really very chilly water.
Celebrities across the globe are filming themselves pouring ice buckets over their heads to raise awareness and money for illness ALS, also known as Lou Gehrig's disease and Motor Neurone Disease, a condition that attacks the spinal cord.
Here are a few of the best...
While plenty of celebrities have been quick to embrace the ice bucket, Guardians of the Galaxy star Chris Pratt tried his best to avoid his inevitable soaking. Not that it worked.