The Duke and Duchess of Cambridge and Prince Harry want to "help change the national conversation" on mental health.
So, they've announced they're leading a campaign called Heads Together. It's the biggest single project they have undertaken together.
And it's a partnership with charities which have experience in tackling stigma, raising awareness, and providing help for people with mental health challenges.
How great is the bit in the video where Wills and Harry have a right laugh while taking photos of each other?
FYI, the campaign will be the Virgin Money London Marathon Charity of the Year in 2017.