Ernst Chladni was a German physicist and musician, most known for the Chladni Plates – an experiment which still looks intriguing to most of the people. This experiment is a good and beautiful way of visualizing the nodes and antinodes on a vibrating surface. Originally this experiment was obtained with a metal plate with some sand on it that is driven into various resonant states with the use of a violin bow. The plate itself like everything in the physical world would have a certain resonant frequency, and when the frequency of the vibrations matches or is proportional the resonant one, these interesting shapes as in the picture below would be formed by the sand.
You can actually watch a modern recreation of the original experiment on youtube: