You can't see it, but you still breathe it in: Air pollution is an invisible threat to millions of people living in urban areas, and many lives are lost prematurely because of it. Increased efforts are being made, not the least in the Nordics, to tackle this health issue through urban design. Researchers are cooperating with urban developers to change transport systems, reduce pollution around schools, and help citizens by measuring the air quality from neighborhood to neighborhood, even from street to street.