From press release:

"Mise En Abyme is a term that refers to a story within a story. It functions the same way that two mirrors do when you face them towards one another, revealing an infinite world of reflecting light where before there was only a few square yards of empty space. Only when the two mirrors are facing each other does the focus of attention shift away from our own reflection and onto the mirror itself- forcing us to wonder about, and test the properties of, it's reflectiveness.

Images below are from install at the Pigeon Wing in London.