The Thread and the Labyrinth
Every nine years Athens sent seven young men and seven young women to feed the Minotaur in the Cretan labyrinth. Theseus volunteered; Princess Ariadne fell for him at first sight and slipped him a ball of thread. Unspooling it as he went, he killed the Minotaur bare-handed and retraced the thread back out — the simplest tool, a priceless idea.