In school? I forget, not sure. I actually enjoyed the biology experiments better than the Physics ones back then, funnily enough. I remember growing plants under different conditions in my home, and seeing the different results which was pretty cool.
Now it’s probably the new LIGO experiment. Two black holes collide a billion years ago resulting in massive gravitational waves being spread out in space. A billion years later, in 2016, us humans detect the Earth marginally shrinking for a very small amount of time as a result of these waves. Pretty cool experiment to be able to detect that.