Oil Ball inside a spinning bearing.

As the title suggests this is a tiny ball of oil rolling around inside a plain white metal bearing. Normally when I squirt the oil in to aid in polishing the bearing with steel wool it quickly flattens out against the bearing's surface but if i squirt in just the right amount of oil it forms a ball and rolls around the bore like in the video. I'm not sure how this works so maybe someone out there has a answer.