In 1870, the British Royal Society in London, England witnessed a thought-provoking demonstration given by natural philosopher, John Tyndall. Tyndall, using a jet of water that flowed from one container to another and a beam of light, demonstrated that light used internal reflection to follow a specific path. As water poured out through the spout of the first container, Tyndall directed a beam of sunlight at the path of the water. The light, as seen by the audience, followed a zigzag path inside the curved path of the water. This simple experiment, illustrated in Figure 1.1, marked the first research into the guided transmission of light.