The Brownian Motion

The discovery of Brownian motion was made because of the pursuit to understand life. Einstein said, what if atoms and molecules really exist and they're just too small for us to see? They must be moving. If an object is small enough, then there's a possibility that you might get more collisions from the left than from the right. That would be why the object would move around randomly. In some sense, it's a tracer for the fluctuations of the atoms and molecules that are too small for you to see.