Jessica Biel and Into The Wild star Emile Hirsch have begun their charity climb up Africa's Mount Kilimanjaro - to raise cash and awareness about the world's chronic water shortage.
The two movie stars have been joined by actress Isabel Lucas and pop stars Santi White, Lupe Fiasco and Kenna on the trek to the top of the 19,340-foot peak.
The star-studded group began the climb on Thursday (07Jan10) and are using the latest social networking technology to update fans and followers along the way.
They'll be posting posting clips, photos and 'tweets' on the Summit on the Summit website.