Like many Hollywood success stories, Mark Ruffalo went through the "struggling artist" phase and earned his place at the table. Unlike many of his peers, he had to deal with devastating hardships and health problems along the way. When presented with his laidback attitude and goofy grin, it's hard to imagine all he's been through. It only makes his success and positive influence even more admirable. He's gone from high school plays to the raging Hulk, all while raising three children and advocating for the environment.
Click through the following gallery to find out how he got to be the actor, producer, director, writer, and activist he is today.