Take one part challenge, one part charity, sprinkle in some celebrity and cook on high with Facebook. Voilà: You have the Ice Bucket Challenge -- the viral phenomenon that's likely taking your Facebook feed by storm.

The concept -- which you know by now consists of people dumping a bucket of ice water on their heads and challenging others to do the same -- has spurred millions of dollars in donations for the ALS Association, and is among the biggest viral hits in Facebook's history: The company said on Monday that 2.4 million videos "related to the ice bucket challenge have been shared" on the social network, and more than 28 million people have posted, commented or liked a post relating to the challenge.

"Marrying the Internet's love of challenges with donation and charity is a stroke of genius," Neetzan Zimmerman, a former editor at Gawker who's widely considered an expert in viral phenomena, told The Huffington Post. "There's no other way to say this -- it's absolutely pure brilliance."



Justin Timberlake completes the challenge.

The nature of the Ice Bucket Challenge is, in itself, inherently spreadable -- it's easy to do, you're being called out in a public forum, and there's a chain letter-like "pass it on" nature in tagging other people.

"People want to look good to others, so it’s hard to turn down a prosocial cause," Jonah Berger, the author of Contagious: Why Things Catch On, wrote in an email to The Huffington Post. "ALS is a great cause, so when someone asks you directly to do this, it’s hard to turn them down without seeming like a bad person."

The Internet, after all, "revolves around" challenges, Zimmerman said, referring to the "cinnamon challenge," where people would upload videos of themselves attempting to gulp down a spoonful of cinnamon, and planking, where people would lay down in ridiculous places for the sake of showing they completed the challenge.

The Ice Bucket Challenge also has an element of hashtag activism, or slacktivism, said Zimmerman, who's now the editor in chief of Whisper, an app that allows people to share secrets anonymously. You can do something from your computer -- or from your yard -- that makes you feel good, but doesn't actually do anything. (In a versions of the challenge, you can get out of the donation if you douse yourself, which is something the campaign has been criticized for.)

Who can forget Kony 2012 -- and its hashtag #stopKony? -- the short video about the African warlord that spread on Facebook and Twitter, but was also criticized for, among other reasons, not actually doing anything other than "raising awareness"? This was also a criticism of the LGBT marriage equality movement last year, when 3 million people changed their Facebook profile pics to equal signs.

The Ice Bucket Challenge campaign has been great for the ALS Association, a nonprofit organization that does research and provides help for those with the debilitating neurological disorder, also known as Lou Gehrig's disease. The organization said Tuesday morning that it's received $22.9 million since July 29 -- up from $1.9 million over the same period last year. And the donations are coming not only from existing donors, but from nearly half a million new donors, the group said.

"If you're doing the same thing they're doing, it's as if you can stand in for them," said Jennifer Cool, an anthropologist at USC who studies Internet culture and history. "You too can be in the shoes of Lady Gaga or Bill Gates."

And, of course, there's the showing off factor. Facebook is, at its core, a place to show off and promote yourself, filled with incredible vacation photos, reminders to all that you're in love and musings about challenges overcome (ideally while on vacation, like hiking in South America). You may have some friends who've seemed eager to show off their bikini or swim trunk bodies in their Ice Bucket Challenge videos.

At this point, some celebrities seem to be trying to one-up each other. Bill Gates released a highly produced (yet charming) video of himself designing an intricate method of dumping water on himself. Hockey player Paul Bissonnette, for some reason, had a helicopter drop glacier water on him. And Tyler Perry's video seems to have an element of "check out this ridiculous pool I'm standing in."

Celebrities also seem eager to name drop in their nominations. "I know where you live," Oprah says to Steven Spielberg as she nominates him to take the challenge.

Like all viral phenomena, the Ice Bucket Challenge may fade away just as quickly as it blew up.