We know that in physics, according to Brownian motion, if we take a molecule and place it inside a fluid, the molecule will collide with the atoms or molecules of that fluid. And as a result, that molecule in the fluid will experience random and rapid motion. So let's conduct the following thought experiment. Let's suppose we take a container shown in the black region. And inside that container we have a certain fluid. So the atoms of that fluid are shown by these blue dots.