This is mesmerizing: For their art installation Sonic Water, Sven Meyer of Elfenmaschine and Kim Pörksen of Piece of Cake, put a cap of water on a vibrating plate on top of a loudspeaker. The result is a gorgeous music visualization based on cymatics (or the study of visible sound and vibrations).
Link - via designboom (Photos: Diephotodesigner.de and Kim Pörksen)