Hu Weiwei and Xia Yiping

Hu met Xia in 2012, when she was a journalist and he was working on connected cars for Ford in China. She requested an interview -- then stood him up, but they still kept in touch. Three years later, Hu persuaded Xia to pivot from cars to bikes. Along with Wang Xiaofeng (who's over 40) they started Mobike, now the world's largest bike-sharing company with more than 25 million daily rides in 160 cities worldwide, plus more than $1 billion in funding from the likes of Tencent, Sequoia, and Warburg Pincus.