Mark Zuckerberg has posted a video to his Facebook page that shows him completing the 'Ice Bucket Challenge' in aid of ALS.
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease, the most common of five motor-neurone diseases. Symptoms include muscle spasticity, muscle atrophy and difficulty swallowing, speaking and breathing.
The Ice Bucket challenge began in a similar fashion to the 'Neck Nomination' trend, where users would nominate friends to complete the challenge within 24 hours.
The challenge evolved to take on aspects of the positive #NoMakeUpSelfie campaign - and tagged users now have 24 hours to complete the challenge or donate $100 to charity. Users can choose to do both if they wish.
Zuckerberg posted the video, telling fans that Governor Christ Christie of New Jersey nominated him.
He then dumped the bucket of ice-cold water over his head, saying "that's cold!"
He in turn nominated Bill Gates, Sheryl Sandberg and Reed Hastings .
Sheryl Sandberg is the Chief Operating Officer (COO) of Facebook, while Reed Hastings is the CEO of Netflix.
They have 24 hours to complete the challenge, donate to the ALS Foundation or both.
The ALS Association is the primary not-for-profit tasked with "aggressively searching for new treatment and cures", "co-ordinating multidisciplinary care" and providing assistance to people with ALS.
ALS is also known (in the US) as Lou Gehrig’s Disease.