In a surprise announcement today, Mark Zuckerberg and his wife Priscilla Chan have pledged to donate 99 percent of their Facebook shares to the cause of human advancement. That represents roughly $45 billion at Facebook's current valuation, making it one of the largest pledges in history. The money will go to the Chan Zuckerberg Initiative, a company that Facebook says will "pursue its mission by funding non-profit organizations, making private investments and participating in policy debates, in each case with the goal of generating positive impact in areas of great need."

The full amount is pledged over the course of Zuckerberg's life, and the Facebook CEO plans to maintain his majority voting position "for the foreseeable future," according to an SEC filing. In the immediate future, the Initiative will be funded by a series of three annual donations made from the sale of Zuckerberg's stock, at no more than $1 billion each year. Profits made by any of the Initiative's investment will be used for additional work to advance its goals.

The initiative's announcement, which is written as a letter to Zuckerberg and Chan's newborn child, focuses on two central goals: advancing human potential and promoting equality. The first goal is defined as "pushing the boundaries on how great a human life can be," including initiatives on medicine, economic opportunity, and access to information. The second group of projects focus more on alleviating poverty and empowering traditionally underrepresented groups. "Our society must do this not only for justice or charity, but for the greatness of human progress," the letter reads.

"Our society must do this not only for justice or charity, but for the greatness of human progress."

Those goals fit into a number of charitable projects Zuckerberg and Chan have already engaged in. Last year, the couple pledged $25 million dollars to fight the spread of Ebola, with the explicit aim of preventing a larger public health crisis "like HIV or polio." Zuckerberg also individually donated $100 million to the Newark public school system, although a significant portion of the money was swallowed up by bureaucratic inefficiencies.

Some of the initiative's goals also align with Facebook's Internet.org project, which aims to establish zero-rated internet access in poor countries. "Many of the greatest opportunities for your generation will come from giving everyone access to the internet," the letter reads. "The internet is so important that for every 10 people who gain internet access, about one person is lifted out of poverty and about one new job is created." Other priorities include community education and childhood healthcare.

The project bears significant resemblance to the Bill and Melinda Gates Foundation, another prominent philanthropy effort built on a Silicon Valley fortune. Launched in 2000, the Gates Foundation currently has an endowment of $44 billion, just shy of the donation pledged by Zuckerberg and Chan. Zuckerberg partnered with Gates earlier this week to fund clean energy research in the wake of the Paris Climate talks, and have worked together on education initiatives in the past. Melinda Gates has already replied to the couple's post, saying "the example you’re setting today is an inspiration to us and the world."

Correction December 2nd, 12.30 AM ET: This story previously indicated that Chan and Zuckerberg were giving their fortune to charity. Facebook has confirmed that the Chan Zuckerberg Initiative is an LLC, rather than a charitable trust.