Cesium-137 is a radioactive isotope of the element cesium, produced during nuclear fission processes, such as those in nuclear reactors and atomic bombs. It has a half-life of about 30 years, meaning it takes that long for half of the substance to decay into a stable form. This isotope emits beta and gamma radiation, making it useful in various applications, including medical treatments, industrial gauges, and as a tracer in environmental studies. However, due to its radioactivity, Cesium-137 must be handled with care to prevent exposure and contamination.