Thorium 229 based nuclear clocks
jerrycards.com
2 threads
Side question: In a past life I was inside a optics lab for a physics course, and the photo look very realistic, I'd even would call it real. But lasers are not visible unless you add fog or something, so I'm confused.
You don't need a lot of fog if you have a long exposure.
Two teams have independently gotten a new kind of ultra precise clock working based on isomers of the thorium 229 nucleus. Currently not as accurate as atomic clocks but they have the potential to redefine the metric second.