Jack Dorsey, Co-founder of Twitter and Square

On October 4, 2015, Jack Dorsey was named Twitter’s permanent CEO. Ten days later, Square was listed on the New York Stock Exchange. He was CEO of that company too.

If that’s not parallel entrepreneurship then I don’t know what is.

Twitter itself was born from a parallel track within Odeo, a once-popular podcasting service. Dorsey approached the founders with his idea for a status updating service that would fit within the constraints of the SMS text messaging system.

In March 2006, after several iterations on their product, Jack Dorsey posted the first-ever tweet: “just setting up my twttr.” He became Twitter’s first CEO and over the next ten years he would be its chairman, interim CEO, and once again its permanent CEO.

Dorsey originally lost his CEO position for leaving work early to do yoga and explore fashion design. So in May 2010, while he was chairman of Twitter, Dorsey launched Square with a co-founder. Square allowed shop owners to accept debit and credit card payments by swiping cards on a device attached to a smartphone.

In July 2015, Dorsey was promoted from chairman to interim CEO of Twitter and he continues to serve both Twitter and Square as CEO.