Actor Mark Ruffalo just posted a shirtless photo of himself on Twitter to increase awareness of breast cancer in men.

Known for his social activism as well as his onscreen performances, Ruffalo posted the image in support of One For The Boys' #InTheNipOfTime campaign:

Ruffalo wasn't the only male celebrity to join in on the fun. "Fantastic Four" actor Ioan Gruffudd, "Snakes on a Plane" star Samuel L. Jackson, and "Harry Potter" star James Phelps shared photos of themselves for the campaign, and many other men did the same, including some male breast cancer victims:

Male victims of breast cancer in America.

#InTheNipOfTime comes at the tail end of Breast Cancer Awareness Month and right before Movember, a month dedicated to men's health issues.

According to the Centers for Disease Control and Prevention (CDC), 405 men in the U.S. died of breast cancer in 2012. That same year, 2,125 men in the U.S. were diagnosed with breast cancer.

For more information on breast cancer in men, go to the American Cancer Society's website.