Facebook founder and CEO Mark Zuckerberg has just videoed himself tipping an ice bucket over his head and posted it online. Why? Because New Jersey governor Chris Christie told him to. And also for charity.
Mr Zuckerberg was taking part in the ice bucket challenge, which is aiming to raise awareness of the neurodegenerative disease Amyotrophic lateral sclerosis (ALS) through a viral campaign. These are the rules of the challenge, as described by the ALS Association.
The challenge involves people getting doused with buckets of ice water on video, posting that video to social media, then nominating others to do the same, all in an effort to raise ALS awareness. Those who refuse to take the challenge are asked to make a donation to the ALS charity of their choice.
Here's Mark Zuckerberg taking the challenge - and nominating Bill Gates.
Your move, Gates...