It has been a long road for Justin. He started in 2004 with Kiko, an online calendar, very similar to Google Calendar. The only really notable things about that startup were it was very early on in this online web application world and it got Justin and team into Y Combinator, which set him on the entrepreneurial career.
From there, the team started justin.tv, as an attempt to make their own reality show on the internet. Although that was a terrible idea that mostly failed, it eventually turned into a platform for anyone to live broadcast their own live video, which became Twitch.tv and in 2014 sold to Amazon for a lot of money.
Justin burned out after about 10 years of doing startups and decided to join Y Combinator and be a partner there, but after a few years of investing in YC startups, he realized being an investor full-time wasn't really for him at that point in life. He was not learning anything anymore.
He started thinking of new ideas and eventually settled on Atrium.