Mark Zuckerberg and his wife Priscilla Chan pledged to give away 99% of their Facebook shares, valued at $45 billion, to charitable causes over their lifetime. They announced this in an open letter to their newborn daughter, committing to donate most of their fortune to issues like health, education, and equality. While Zuckerberg will remain CEO of Facebook, he plans to focus on philanthropic work through their new Chan Zuckerberg Initiative. The pledge establishes them among philanthropic leaders like Buffett and Gates who have donated most of their wealth.