Deionized water and purified water is water that has undergone a physical process to remove all of its impurities. Deionized and purified water are the most common types of pure water but water can also be purified by other methods like microfiltration, carbon filtration, reverse osmosis, ultrafiltration, ultraviolet filtration and electrodialysis. In the past few years’s different processes involving one or more of the above methods combining them together to produce perfectly clean water. This results in the contaminants being in such small quantities, that they have to be measured in parts per billion or even parts per trillion. This water is used for many purposes and applications including scientific laboratories and is also used in the engineering industry. Purified or deionized water can be produced in a range of different purities, each having its own application.