It's November, aka Movember, and that means men all around the world are getting hairy for charity.
Movember began 8-years ago in Melbourne, Australia, when a group of men decided to grow moustaches throughout the duration of November to raise money and awareness for prostate cancer prevention and treatment, as well as depression in men.
The group then formed the Movember Foundation, which has inspired 1.9 million men to get mustachioed for the cause and raised $299 million so far.
Here's the deal: men who decide to participate become known as "Mo Bros". Men who started the month clean shaven grow a moustache for the duration of the month, taking pictures of their progress and uploading it to a Movember profile page.
There are as yet no Mo Bros registered for Castro Valley, though there are some for Alameda, Fremont, Pleasanton, Dublin and Concord.
Funds raised are donated to a number of men's health programs, including the Prostate Cancer Foundation and the LIVESTRONG Foundation, as well as awareness and education programs and a global health plan.
But Movember isn't just for men. Women can participate too — without having to grow moustaches.
"Mo Sistas play a vital role in the success of Movember by supporting and encouraging the men in their life to get involved, and participating in raising funds and awareness themselves," explains Movember US.
Need help deciding on a moustache style? Check out the Movember style guide.
Will you participate in Movember? Are you pro or con moustache? Share your moustache story here by clicking the "upload" button above.