Check out this demonstration of Chaldni plates!
The demonstrator changes the frequency by changing the position of the bow and his finger at the edge. For every frequency a different sand pattern arises according to the vibration pattern of the plate. Where there are few vibrations, called nodes, the sand settles, and where there are a lot of vibrations, called antinodes, the sand scatters. These resonance patterns arises for any instrument with a resonant body, including bells.
Furthermore, an instrument, such as the bell, will vibrate at several different patterns at the same time. These different vibration patterns are what create the multiple overtones present in any given pitch. Below you see an exaggerated scheme of just a few of the vibration patterns for a bell. (There are six half profiles presented.) The “K’s” stand for nodes and the “B’s” stand for antinodes. Try imagining a bell vibrating all of these different ways at once!