For years, union membership has been shrinking in the United States and many other countries. But recently we've seen a resurgence, with employees in sectors like retail, hospitality, and media organizing to collectively bargain for better pay, benefits, and job flexibility. Thomas Kochan, a professor at the MIT Sloan School of Management, has long studied how unions affect individual, team, and corporate performance. He explains why some fears about them are overblown, how workers form successful ones, and how leaders can partner with these groups to ensure the best outcomes for everyone.