Worms that live in the human intestine or skin leave most people feeling nothing but disgust. But these parasites can also be useful: They are apparently able to keep the human immune system in check in an intelligent way. This property could help precisely those patients whose immune systems “go crazy,” attacking even the body’s own tissue and missing invasive pathogens.

They measure sulfur dioxide and nitrogen oxide, carbon monoxide, ozone, benzene, and particulate matter. Some of the things they record are odorless, while others have a distinctive unpleasant smell – and yet, the Berlin Senate Department for Urban Development and the Environment has given its air quality measurement network an evocative name: BLUME, German for “flower.”