Oversimplified TLDR: They put rolled gold into a Prussian Red solution, waited a couple of months and then rinsed it in Palmolive solution? It is possible the

Oversimplified TLDR: They put rolled gold into a Prussian Red solution, waited a couple of months and then rinsed it in Palmolive solution? It is possible they did not obtain the Prussian Red in the good old way of cooking blood and bones with potash but ordered it from the Internet: https://www.morphisto.de/en/shop/detail/d/KIT%3A_Ätzmittel_nach_Murakami/15207/ https://www.morphisto.de/en/shop/detail/d/KIT%3A_Ätzmittel_n... On a more serious note, it is surprisingly easy to create mono-molecular films. Allegedly Benjamin Franklin made one on Mount Pond near Clapham Common in 1774.