The Casimir Force and the associated effect were the original proof that even a pure vacuum has something in it. The experiment was to put two metal plates in a vacuum, suspended, only a tiny distance from each other. And a force was detected between them. The plates weren’t being charged from the outside, there was no leak in the container. The truth is that even in a vacuum energy fluctuations occur that have the theoretical ability to create particles that cease to exist almost instantly. But in this moment of being the particles can exert a force on both plates either to pull them together or push them away.
This is entirely irrelevant in everyday life but when people are designing electronic chips that are reducing to the nanoscale it becomes something that either risks being a hindrance of could possibly be used as an advantage. The current aim is to apply this affect in optomechanically induced transparency (OMIT). These materials would be able to control their opacity based on minute electric signals and now research also implies that the Casmir effect could be used in a similar way.