Cesium is a highly reactive metal that is used in a variety of applications. It is often used in atomic clocks because it has a very stable energy state that can be used to measure time very accurately. Cesium is also used in certain medical imaging procedures and in drilling fluids for oil and gas wells. Additionally, cesium can be used to remove residuals from vacuum tubes, and it can be used to catalyze several types of organic reactions. However, cesium must be handled with extreme caution because of its reactivity and potential toxicity.