The Cheerios Effect is the name the scientific community has given to this phenomenon. When cornflakes or oats are mixed with milk and stirred, they tend to clump together. Why does this happen? Can physics explain this?
Assuming your question is essentially: "Why do the flakes actually 'clump' together ?", the answer is one that involves probability.
Suppose you have only two wet corn-flakes on the surface of milk isolated from each other. Say somehow they start moving toward each other. As they come together, they stick. Now, once stuck, the flakes will not seperate from each other on their own. (probably because they have attained a state of lower energy). In other words, the probability of them seperating is literally zero.
Now let's say there are many such flakes which are isolated from each other on the surface. Let's start strirring the milk in a random fashion and not necessarily in a circular manner. As you stir randomly, the flakes start moving in random directions on the surface of milk. Some may move toward each other, and some opposite. But those which move towards each other are by fate destined to stick and once stuck they don't move apart. Therefore, there are many probabilities that the flakes may come together, but there is zero probability that they come apart. That is, the flakes which are stuck remain stuck even though there may be other unstuck flakes randomly moving about on the surface. In time, even those flakes will stick to the ones which are already stuck. Thus, the flakes finally 'clump' together.
Hope it helped !