Social Mirror is a web application that helps Twitter users interactively explore the politically active parts of their social network. Worsening political polarization over the past several years has exacerbated ideological echo chambers, which in turn have further fueled polarization by widening knowledge and empathy gaps between disparate groups. We hope digital tools like Social Mirror can help inspire self-reflection, and ultimately, intellectual humility by providing people with a new view of their social media ecosystems and helping them form new network connections.