Cesium 133 facts

While investigating facts about Cesium 133, I found out little known, but curios details like:

One second is measured as exactly the duration of time it takes for 9,192,631,770 oscillations to occur between the nucleus and the outermost electron in the Cesium 133 atom, and that this forms the basis on how we measure all time.

In my opinion, it is useful to put together a list of the most interesting details from trusted sources that I've come across. Here are 1 of the best facts about Cesium 133 I managed to collect.