Facebook co-founder and CEO, Mark Zuckerberg, on Monday announced that his wife, Priscilla Chan, has given birth to a baby girl named August.

The 33-year-old made the announcement on his social media platform.

“Priscilla and I are so happy to welcome our daughter August!” he wrote in a Facebook post.

Zuckerberg’s announcement about August’s birth was accompanied by a photograph of the family.

He also included a letter to his daughter from himself and his 32-year-old wife, expressing hopes that she would take time to enjoy her childhood.

“Childhood is magical,” reads the letter. “You only get to be a child once, so don’t spend it worrying too much about the future. You’ve got us for that, and we’ll do everything we possibly can to make sure the world is a better place for you and all children in your generation.”

He also highlighted his optimism for her future, explaining that “even though headlines often focus on what’s wrong, we still believe these positive trends will win out.”

Zuckerberg and Chan wrote a similar letter to their first daughter, Max, upon her birth in 2015.