Accel owns 23.8% of Slack and Andreessen Horowitz owns 13.2% of the company. Slack co-founder and CEO Stewart Butterfield controls 8.4%. _Accel invested $1.5M in seed round around 2009_ Venture firm Accel is known for making one of the most lucrative start-up bets in history, parlaying an early $12.2 million investment in Facebook into a stake worth more than $9 billion at the time of the company’s IPO in 2012. #VCs #whos_rich #pub