Facebook founder Mark Zuckerberg and his wife Priscilla Chan have had a baby girl - and have announced they are giving away 99% of their 45 billion-dollar (£30bn) fortune to good causes.
The couple wrote an open letter which they shared on the social media platform which he invented, where they spoke of creating a better world for their first child, Max, and future generations.
The proud parents vowed to use their wealth to cure disease, harness green energy, reduce poverty and promote equality.
In a Facebook post on his page, together with a photo of them gazing with love at their new daughter, the couple wrote: "We are committed to doing our small part to help create this world for all children.
"We will give 99% of our Facebook shares - currently about 45 billion dollars - during our lives to join many others in improving this world for the next generation.
"Thank you to everyone in this community for all your love and support during the pregnancy.
"You've given us hope that together we can build this world for Max and all children."
The move echoes that of Microsoft co-founder Bill Gates and his wife Melinda who have set up a foundation to do good around the world.
In the lengthy letter to Max, Mr Zuckerberg, 31, said: "Your mother and I don't yet have the words to describe the hope you give us for the future.
"Your new life is full of promise, and we hope you will be happy and healthy so you can explore it fully.
"You've already given us a reason to reflect on the world we hope you live in.
"Like all parents, we want you to grow up in a world better than ours today."
He said that while headlines were often negative,"in many ways the world is getting better".
The note continued: "Health is improving. Poverty is shrinking. Knowledge is growing. People are connecting. Technological progress in every field means your life should be dramatically better than ours today.
"We will do our part to make this happen, not only because we love you, but also because we have a moral responsibility to all children in the next generation."
The couple went on to promote equality, to explain how they believe in medical advances and a vision of a world without disease.
They said: "This mission - advancing human potential and promoting equality - will require a new approach for all working towards these goals.
"We must make long-term investments over 25, 50 or even 100 years."
Mr Zuckerberg wrote about huge advances in education that will come about.
"Your mother and I have both taught students and we've seen what it takes to make this work," he said.
And the couple had a vision of spreading access to the internet to more people around the world, as more than four billion people are not online, to increase prosperity.
He said: "It will take inventing new technology to make the internet more affordable and bring access to unconnected areas.
"It will take partnering with governments, non-profits and companies. It will take engaging with communities to understand what they need.
"Good people will have different views on the best path forward, and we will try many efforts before we succeed.
"But together we can succeed and create a more equal world."
He said he will continue in his role as Facebook CEO for "many, many years" but vowed to start work now on building a better future.
The letter finished: "Max, we love you and feel a great responsibility to leave the world a better place for you and all children.
"We wish you a life filled with the same love, hope and joy you give us. We can't wait to see what you bring to this world.
"Love, Mom and Dad."