Dong Mingzhu is sometimes called “the Iron Lady,” and it’s with good reason. She rose through the ranks at China’s largest air conditioning company—she got her start selling window units after the death of her husband—to become the boss in 2001. She admitted earlier this year that she hasn’t taken a day off from the job in more than two decades. In recent years, she has focused on diversifying the business and wading into electric vehicle and smartphone markets. But, the AC market hasn’t chilled just yet: Profits rose 16% at the company last year, and Gree’s stock is up 54% in 2017.