It was the birth announcement to top all birth announcements. In telling the world about the birth of their newborn baby, Mark Zuckerberg and Priscilla Chan also pledged to give away 99 percent of their Facebook shares – worth an eye-popping $45 billion – to philanthropic efforts during their lifetime.

Mark Zuckerberg and Priscilla Chan to give away 99 percent of their Facebook stock, worth $45 billion

It’s probably telling that the first example they describe in depth is medical science.

“Dear Max,” the 2,234-word open letter to their newborn daughter begins. “Your mother and I don’t yet have the words to describe the hope you give us for the future… Like all parents, we want you to grow up in a world better than ours today.”

The couple, who met while attending Harvard University, said that they believe the world should be dramatically better for their child than it was for them.

“We will do our part to make this happen,” they said, “not only because we love you, but also because we have a moral responsibility to all children in the next generation.”

In outlining their vision for how they would achieve this, Facebook CEO Zuckerberg, 31, and Chan, 30, a doctor, said they were focusing on two ideas – advancing human potential and promoting equality. While they didn’t announce any specific projects or donations for the effort that they are calling the Chan Zuckerberg Initiative, they outlined personalized learning, curing disease, connecting people and building strong communities (in that order) as being priorities.

Here’s what they said about medical science:

Consider disease. Today we spend about 50 times more as a society treating people who are sick than we invest in research so you won’t get sick in the first place.

Medicine has only been a real science for less than 100 years, and we’ve already seen complete cures for some diseases and good progress for others. As technology accelerates, we have a real shot at preventing, curing or managing all or most of the rest in the next 100 years.

Today, most people die from five things – heart disease, cancer, stroke, neurodegenerative and infectious diseases – and we can make faster progress on these and other problems.

Once we recognize that your generation and your children’s generation may not have to suffer from disease, we collectively have a responsibility to tilt our investments a bit more towards the future to make this reality. Your mother and I want to do our part.

Curing disease will take time. Over short periods of five or ten years, it may not seem like we’re making much of a difference. But over the long term, seeds planted now will grow, and one day, you or your children will see what we can only imagine: a world without suffering from disease.

The couple has been generous – and creative – with its philanthropy in health care in the past. In October 2014, they donated $25 million to the Centers for Disease Control Foundation to help fight Ebola.

“We believe our grant is the quickest way to empower the CDC and the experts in this field to prevent this outcome.
Grants like this directly help the frontline responders in their heroic work. These people are on the ground setting up care centers, training local staff, identifying Ebola cases and much more,” Zuckerberg wrote in a Facebook post at the time. “We are hopeful this will help save lives and get this outbreak under control.

Earlier this year, Zuckerberg and Chan donated $75 million to San Francisco General Hospital, a new public hospital, to help out with costs for critical equipment and technology. Chan, a pediatrician, has taken time off from her practice to start a private school in Northern California for low-income children that will give them access to free health care as part of their education.

A number of their technology peers have also given generously to medicine and science. Napster co-founder Sean Parker’s name is on a new center at Stanford University dedicated to finding a cure for allergies. Google co-founder Sergey Brin and his wife Anne Wojcicki, who are separated, have donated many millions to fight Parkinson’s disease. And Peter Thiel, the eBay co-founder, has given grants to a number of scientists and medical tech startups that aim to extend human life.

Zuckerberg and Chan’s letter echoes some of the ambitious thinking about philanthropy articulated by other young, wealthy Silicon Valley couples, Cari Tuna and her husband Dustin Moskovitz in particular. Tuna and Moskovitz, who is also a Facebook co-founder and is estimated to be worth $9.9 billion, have also pledged to give away most of their wealth in their lifetimes and have said they are looking to make an impact that will benefit future generations. They have also highlighted science as one of the main areas they are exploring with their philanthropy in addition to U.S. policy, global catastrophic risks and international aid.