Each good chromatographer wants to implement proper temperature control. For this purpose, column thermostats have evolved from simple units just providing a fixed temperature to high-tech devices. Elevated temperatures, well above the boiling point of the mobile phase, become more and more applied. Consequently, mobile phase preheating prior to entering the column as well as post-column mobile phase cooling prior to entering the detector becomes mandatory. In addition, viscous heating is a much discussed topic in Ultra High Performance Liquid Chromatography (UHPLC). When pressures increase to values far above 400 bar, friction between column and mobile phase generates high amounts of viscous heat and, thereby, an additional temperature increase inside the column.