Have you ever eaten cereal and noticed how the last few floating pieces tend to stick together in the bowl? Scientists call this phenomenon the “Cheerios effect.” Now, researchers at Brown University in Rhode Island have figured out exactly why cereal tends to clump together.

Many types of cereal float because their pieces aren’t heavy enough to break through milk’s surface tension—the attractive force between molecules on a liquid’s surface. But the weight of each piece does create a slight dip in the top of the milk. When two pieces of cereal drift near each other, their indentations merge into a bigger depression. The pieces slip into that larger depression and end up stuck together—making it easier for you to scoop up the last few bites of your breakfast.