The world has never been so urban. And humankind has never had so much riding on the success of our cities, which today generate over 80% of global GDP, according to the World Bank. They also produce 70% of greenhouse gas emissions. And as people continue to flock to urban centers in search of opportunity, the challenge of keeping these environments workable (and livable) continues to grow. To better understand how cities are adapting, our reporters went deep in three major metropolises: San Francisco, Shenzhen, and Toronto. We also solicited “city fixes” from a range of experts. Read on for insights into our shared urban future.