Chinese fashion retailer Shein isn't just fast — it's ultrafast. The $100 billion company has captivated young shoppers by using social media to market its dirt-cheap clothing.

However, despite all the success, not much is known about Shein's sales, supply chains or algorithms. Critics are now sounding the alarm over the environmental and social impact of Shein, and what its rise means for the future of fashion.

Today, Vauhini Vara, a journalist who has written for the New Yorker, Wired and the Wall Street Journal, explains the alluring world of Shein, and what ultrafast fashion means for the planet.