Step inside Slack's light-drenched New York City office

Slack is one of the most closely watched startups in Silicon Valley, and now it has a home base in New York, too.

The three-year-old chat app maker boasts 4 million daily users, from employees at media companies like Business Insider, to workers at companies like IBM, who use it to coordinate code-building.

The San Francisco-based company has raised $539 million dollars from investors including Accel Partners, GV (formerly Google Ventures), and Thrive Capital.

Business Insider was recently invited to tour the company's new East Coast headquarters in New York City. According to Slack, this is where its search, language, and East Coast sales teams will be based.

Check out the highlights below: