A sticky bookmark
Spencer Silver, an American chemist, was trying to perfect a super-resistant glue in the 1970s. While he managed to create a glue that would stick to paper, be removed and reused several times, unfortunately, it was not powerful enough for his requirements. Arthur Fry, his colleague, became interested in the invention and used it to make a bookmark that wouldn’t damage his book. He soon discovered its potential and went on to market Post-its in 1981.