A couple years ago, I saw P. Littlewood give a colloquium on exciton-polariton condensation. To introduce the idea, he performed a little experiment, a variation of an experiment first performed and published by Christiaan Huygens. Although he performed it with only two metronomes, below is a video of the same experiment performed with 32 metronomes.
A very important ingredient in getting this to work is the suspended foam underneath the metronomes. In effect, the foam is a field that couples the oscillators.