Around the world, cities plagued by smog have tried to clear up the skies among the skyscrapers. Discover their successes by comparing photos from before and after changes were made by local governments
Want better willpower? Learn how to just say no with this step-by-step guide on boosting your self-control. In this one-minute video, Ask Smithsonian host Eric Schulze dishes on the science behind willpower – what saps it and what makes it stronger.