How big does a brain need to be to for an animal to be intelligent? Bumblebees show that size does not matter. In a new study, scientists taught buff--tailed bumble bees to push a ball into a goal for sweet rewards. This complex exercise turned out to be simple for the insects, whose brains are a size of a sesame seed. They solved the puzzle just by observing a demonstration, and some even innovated their own ways to perform the task. This behaviour explains how pollinators memorise objects and fly miles to collect nectar. The experiment was conducted by Clint Perry, a cognitive biologist at Queen Mary University of London.