(MoneyWatch) Jack Dorsey, a.k.a. @jack is the Executive Chairman of Twitter, CEO of Square, and a founder of both. The die-hard Cardinals fan was already programming computers before high school. At New York University, he and co-founder Biz Stone came up with the idea for Twitter.
Then on March 21, 2006, @jack sent the first tweet ever: just setting up my twttr. Four years later, Dorsey went on to found mobile payment platform, Square.
Square lets anyone with an iOS or Android device take credit card payments over their smartphone. Dorsey developed the technology after a friend couldn't sell his art to cashless customers.
Dorsey didn't want the form of payment to stand in the way of a transaction, so he created a portable, free, technology that anyone with an iPhone or Droid could access.