Worker bees buzz through Tumblr’s headquarters in the Flatiron district of Manhattan. With so many young employees, who move between glass-walled conference rooms and a rooftop patio, the place is vibrant. Founded by David Karp in 2007 as a medium for short-form blogs and acquired by Yahoo for $1.1 billion in 2013, Tumblr has hosted more than 115 billion posts. Its users, nearly half of whom are ages 13 to 34, according to the company, add 85 million more each day. People use their Tumblrs for all sorts of things, from old-fashioned cat appreciation to sad-kid blogging, but fashion is the platform’s largest area of interest. We visited Tumblr recently in search of tech chic.