Facebook founder Mark Zuckerberg and his wife Priscilla Chan have announced their next big project - probably the biggest challenge they could embark on.
The billionaire tech whizz said last night that the next major focus for their charity, the Chan Zuckerberg Initiative, is to help scientists to "cure, prevent or manage all diseases" by the end of the century. The move follows the couple's pledge to donate almost all of their Facebook shares to good causes over their lifetimes.
"Today, just four kinds of diseases cause the majority of deaths. We can make progress on all of them with the right technology," the Facebook boss said.
"Throughout history, most scientific breakthroughs have been preceded by the invention of new tools to help us see problems in new ways - like the telescope, the microscope and DNA sequencing.
"It's not hard to imagine the modern tools required to accelerate breakthroughs in today's four major disease areas. So we're going to focus on bringing scientists and engineers together to build these new tools and technologies."
Zuckerberg added: "The science initiative is a long term effort. We plan to invest billions of dollars over decades. But it will take years for these tools to be developed and longer to put them into full use. This is hard and we need to be patient, but it's important.
"This is about the future we want for our daughter and children everywhere. If there's a chance that we can help cure all diseases in our children's lifetime, then we will do our part. Together, we have a real shot at leaving the world a better place for our children than we found it."
The pair will invest $3bn (£2.3bn) over the next 10 years to help scientists take on the mammoth task, a generous donation but not a huge chunk out of Zuckerberg's personal wealth - he's the fifth richest person in the world according to Forbes and, as of July, was worth $55.2bn.
Having already topped a poll of the world's favourite technology chief executives in February this year, Zuckerberg's latest announcement will no doubt cement his popularity.