Where do new inventions come from? Almost never from a single flash of genius. Most begin with an idea, which the inventor then tests again and again in a careful experiment. The first try almost always goes wrong in some small, stubborn way. The second attempt often goes wrong in a different way. Each failure, though, teaches the inventor something — what does not work, and why — and points the way toward a better attempt.

This slow path of trying, failing, and trying again is called trial and error. A famous inventor once said he had not failed, but had simply found thousands of ways that did not work. Bit by bit, each version is used to improve the next, until at last something succeeds. Careful workshops keep notes on every attempt, because a failure nobody records has to be discovered all over again by somebody else. Patience matters as much as cleverness, since an inventor who quits at the tenth try never reaches the eleventh. Wonka’s factory runs on exactly this spirit: for every Everlasting Gobstopper that works, there is a Hair Toffee that still needs fixing.

No right or wrong — close the screen and tell someone nearby what happened in this part. Can’t find anyone? Tell yourself out loud. The moment you teach it, you truly understand it.