Mark Zuckerberg is officially a dad!

"Priscilla and I are so happy to welcome our daughter Max into this world," Zuckerberg posted on his Facebook page.

Max is short for Maxima.

To celebrate her birth, he and his wife, Priscilla Chan, plan to donate 99% of their Facebook shares - about $45 billion - to "advancing human potential and promoting equality" through a new organization called the Chan Zuckerberg Initiative.

Zuckerberg will still retain majority voting rights in Facebook.

The new company will fund nonprofits and focus initially on personalized learning, curing disease, connecting people, and building strong communities.

Here's Zuckerberg's full post, including a letter that he and Chan wrote to their daughter about the world they hope she grows up in:

PostbyMark Zuckerberg.