You may or may not have pondered why your breakfast cereal tends to clump together or cling to the sides of a bowl of milk. Dubbed the Cheerios Effect by scientists, the surface of a liquid (in this case milk unless you use something else with your cereal)’s actually forms a type of crater.
This is because the water molecules in the milk are charged and attracted to the glass surface of the bowl (works with ceramic as well) which means that they pan out from the centre of the bowl taking with it some of the mass (and form) of the liquid. This is how the slight crater forms and the flow of water molecules to the inner rim of the bowl take with it some of the floating cereal near the edge.
Read the full article in Live Science