Finished this gift for a friend yesterday! She introduced me to the nuclear semiotics work that was big in the 80s, and involved thinking about how to communicate to future peoples that there might be hazardous material nearby (given the extremely long half-life of nuclear materials) in a distant future where all of our currently spoken languages might be unintelligible and indecipherable. (The scientists’ answer was to genetically modify cats to change color in the presence of radiation, and then plant a legend that if your cat changed color you should move.)