A drop or droplet is a small volume of liquid, bounded completely or almost completely by free surfaces.
A drop may form when liquid accumulates at the lower end of a tube or other surface boundary, producing a hanging drop called a pendant drop. Drops may also be formed by the condensation of a vapor or by atomization of a larger mass of liquid. Liquid forms drops because the liquid exhibits surface tension.
A simple way to form a drop is to allow liquid to flow slowly from the lower end of a vertical tube of small diameter. The surface tension of the liquid causes the liquid to hang from the tube, forming a pendant. When the drop exceeds a certain size it is no longer stable and detaches itself. The falling liquid is also a drop held
together by surface tension.
Source: http:en.wikipedia.org/wiki/Drop_liquid - 25.03.2010
The light is able to show the real beauty of a water drop.