One of our favorite scenes in "The Fault in our Stars" was, um, every single one involving Nat Wolff's hilarious, heartbreaking, and somehow completely realistic Isaac, so imagine our delight when we learned that Wolff was partnering with DoSomething.org for the "Give a Spit About Cancer" campaign!

The 19-year-old actor is trying to get more young people on the national bone marrow donor registry, which matches viable donors to patients suffering from leukemia and other types of blood cancer.

"You can help cancer just using your spit, seriously," Wolff says in a promotional video, after spitting on a swab himself. "Here's the thing, leukemia kills more children every year than any other type of cancer, and most kids actually need a bone marrow transplant to live. 70 percent of children with leukemia rely on complete strangers to give them their transplants, and they need people from 18-25, and that could be you."

(Well, not me.)

Check out Wolff's statements below, and visit DoSomething.org for more information on how you could "Be the Match."