The emotional post of the 33yearold Facebook co-founder’s second child with wife Priscilla Chan, which appears alongside a family photo on Mr Zuckerberg’s Facebook page, focused on the wonders of childhood, expressing hopes that baby August “doesn’t grow up too fast.”“The world can be a serious place. That's why it's important to make time to go outside and play," it reads.“You will be busy when you're older, so I hope you take time to smell all the flowers and put all the leaves you want in your bucket now."The public letter goes on to say: “Childhood is magical. 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 the children in your generation.”Signed“Mom and Dad”,the letter takes a lighter tone to the one they wrote to welcome elder daughter Max when she was born in 2015.