As he says in his very first post, he wants to use the platform to engage with people. “You’re citizens of a very big world—one made smaller and more accessible by technologies and platforms just like this one,” he wrote, adding that Facebook and other similar outlets “have the potential to be incredible forums for constructive debate.”

It’s likely no coincidence that Biden chose today, World Cancer Day, to join the social media site. He wants to use it to talk to people about his Cancer Moonshot Initiative that President Obama tasked him with during his last State of the Union address. The $1 billion initiative aims to do for cancer in just five years what would otherwise take 10 to 15, a very personal project after losing his son to the disease just last year.

He encourages Facebook users to share their thoughts about it and ask questions, which he plans to answer at 3 p.m. today.