In particular, Hoffman said his donation, made on behalf of himself and his wife, Michelle Yee, will directly support the Chan Zuckerberg Biohub, a new laboratory at the University of California at San Francisco that is working on building new tools to fight diseases. Hoffman also said he is joining the Biohub board.

Zuckerberg and Chan initially debuted their philanthropic venture in December 2015, following the birth of their daughter, Maxima. At the time, they pledged to give away 99% of their Facebook stock, then valued at about $45 billion, over their lifetimes. Zuckerberg and Chan’s effort to donate their wealth was initially controversial because the Chan Zuckerberg Initiative was a limited liability corporation instead of a non-profit. Zuckerberg has defended the decision by saying it affords the organization more flexibility when it comes to allocating funds towards various causes. He also said that any money earned by the Initiative would be put back into charitable efforts.

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In September, they pledged to invest $3 billion over the next decade to help cure and manage all human diseases.

Part of that pledge was a $600 million investment in the Biobhub.

Hoffman wrote of his investment in the initiative on LinkedIn: “Early projects with uncertain results can be quickly funded. Moreover, in the same way that Silicon Valley puts a great deal of human capital and shared knowledge at the fingertips of entrepreneurs, Biohub will similarly facilitate communication and collaboration between life sciences experts. Our hope is that richer networks and feedback loops will help accelerate discovery and development of cures for infectious diseases and a wide range of other life sciences challenges.”

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Zuckerberg, in a Facebook post, explained that the Biohub has already started working on two projects. The Human Cell Atlas is a map of all cells that control the body’s major organs that researchers around the world will be able to access. The second project, called The Infectious Disease Initiative, will create new tools for fighting diseases like HIV, Ebola and Zika.