Over 100 years ago, German scientists discovered that the top surface of lake-water was sterile when exposed to sunlight. Investigation led to the discovery of Ultraviolet light. Situated in the electro- magnetic spectrum between X-rays and visible light, Ultraviolet (UV) light has many beneficial properties. UV light is split into four main categories, UV-A, UV-B, UV-C and Vacuum UV. The area between 240 and 280 nanometres (nm) is UV-C, commonly known as the germicidal region.