During World War II, secret messages were passed using invisible ink. The ink was a harmless chemical that appeared as ordinary paper until heat was applied, making the message visible. This ingenious technology was a vital tool for espionage, allowing Allied forces to communicate secretly. What’s fascinating is that the technology behind this wartime marvel has found a new purpose in modern-day convenience: supermarket scanners. The same light-sensitive chemical used to develop invisible ink is now integrated into scanners, allowing them to read barcodes and instantly identify products at checkout. From secretive wartime communications to efficient grocery shopping, the once invisible ink has become a surprisingly prevalent part of our everyday lives.

Prompt:
Think of a scientific discovery or technological advancement that has had a surprising or unexpected impact on daily life, but isn’t widely known. What is it and how has it changed the world in a subtle yet significant way?