Cesium clocks are highly precise timekeeping devices that use the vibrations of cesium atoms to measure time. They work by counting the oscillations of cesium atoms as they transition between energy states when exposed to microwave radiation. This process allows cesium clocks to maintain an accuracy of one second over millions of years. These clocks are essential for various applications, including global positioning systems (GPS) and telecommunications. The International System of Units (SI) defines the second based on the vibrations of cesium atoms, making cesium clocks a fundamental component in the field of timekeeping and scientific research.