Last night, Facebook founder and CEO Mark Zuckerberg took the Ice Bucket Challenge, answering a nomination by New Jersey Gov. Chris Christie and pouring a bucket of ice water over his head on camera and posting it to his wall on Facebook for the world to see.

“That was really cold,” Zuckerberg said after he stopped dripping.

Per the challenge’s rules each person challenged pours a bucket of ice water over their heads, on camera, or donates $100 to the ALS Association, an American foundation dedicated to fighting amotrophic lateral sclerosis, a powerful neurodegenerative disease (often referred to as Lou Gehrig’s disease). If the challenge is accepted and completed, each person also gets to nominate three more people to do the same in 24 hours.

Here’s the video, from Zuck’s Facebook page:

(Here’s a link to it.)

Started in Massachusetts, The Ice Bucket Challenge is sweeping the nation. Yesterday, it was Jimmy Fallon and the Roots (watch that here)., and social media. Zuck isn’t the first tech titan to take a dunk: Yesterday, it was Microsoft CEO Satya Nadella. It’s more than hashtag activism, BostInno’s Hayden Bird reported last week. Now, the ALS Association says that between July 29 and August 12 $4 million have been raised to fight the degenerative disease. This time last year donations topped out at just over $1 million.

Zuckerberg challenged Microsoft co-founder Bill Gates, Facebook COO Sheryl Sandberg and Netflix CEO Reed Hastings to take to the ice next.