Sridhar Ravi was outdoors with his colleagues on a summer day in Germany when a group of bumblebees grabbed his attention. As the bees made their way from flower to flower, they skillfully flew between obstacles, dodging branches and shrubs. Ravi and his team made the gap progressively smaller over time, and observed how the bees’ reactions changed. The study, published in the Proceedings of the National Academy of Sciences, found the bumblebees measured the gap by flying side-to-side to scan it. Some of the bees’ bodies did bump the sides of the narrowed opening—but every one of the 400 recorded flights through the gap was a success.