Stewart Butterfield isn’t a typical Silicon Valley tech billionaire. A philosophy graduate who grew up in a commune, Butterfield went on to be the man behind one of the fastest-growing apps of all time, business messaging platform Slack. And he has more than a few feathers in his cap: as well as his role as Slack's CEO, Butterfield is also the founder of photo-sharing phenomenon Flickr and a former Yahoo employee. But his route to success was anything but ordinary. Here we take a look at the incredible life of Stewart Butterfield.