A chance invention, the eminently useful post-it note teaches us two important lessons about creativity: first, the vital importance of chance to the creative process and second how failure can be a success.

 In 1974, Art Fry, an American chemist, needed a way of keeping his place in his hymn book. He cast his mind back to a strange substance a colleague had created for which they saw no practical use: a glue that did not quite stick. Fry spent over a year devising ways it could be applied to paper slips such that it remained stuck but could be pulled off.  The rest is history.