Emma Stone, Vanessa Williams, Tom Hanks and Samuel L. Jackson are among the celebrities who are uniting to "stand up to cancer."
In a new video PSA, above, the famous faces reveal who they supported on World Cancer Day, which took place on Feb. 4.
Viewers are urged to participate on social media by using the hashtags #istandupfor and #worldcancerday on Twitter, and to visit the Stand Up To Cancer Facebook page.