Dorsey announced this move, appropriately enough, via a pair of Twitter posts: Here, and here.
"I'm giving ~1/3rd of my Twitter stock (exactly 1% of the company) to our employee equity pool to reinvest directly in our people," Dorsey tweeted. "As for me: I'd rather have a smaller part of something big than a bigger part of something small. I'm confident we can make Twitter big!"
Based on Twitter's current closing price of $29.15 per share, Dorsey's just given over about $214 million worth of company stock back to employees.
Better yet, Dorsey actually announced this to Twitter by posting the tweets while on stage in front of the company's employees:
.@jack live tweetstorming a major announcement to both the company and the world at the exact same time. Amazing. pic.twitter.com/CSMtW0VkOF