Mark Zuckerberg and Priscilla Chan say they'll give the vast majority of their fortune to philanthropy.

In a Facebook post (What, you thought Zuckerberg was gonna take it to Medium?) announcing the birth of their new daughter Max, the couple said that they will give away 99 percent of their Facebook shares “to advance human potential and promote equality for all children in the next generation” with a focus on “personalized learning, curing disease, connecting people, and building strong communities.” 

It’s a long letter, but it’s (perhaps unsurprisingly) short on specifics. According to Reutersthe couple’s shares are worth $45 billion.