The 2011 TIME 100

Being a celebrity is like being a 5-year-old in a room with all the adults staring at you. It's easy to spin out of control. But if you redirect the energy coming at you to a cause you care about, it can be very powerful.

In Matt Damon's case, what he wants you to know is that every 15 minutes a child under the age of 5 dies because of a lack of clean water and sanitation and it doesn't have to be that way. Matt, 40, teamed up with Gary White, 48, a longtime expert in water-supply systems, in 2009 and created Water.org. Their message is one of hope; their solutions for providing access to clean water are simple and cost effective. And their work gives us an opportunity to change lives forever.

Danson is an actor and environmental advocate