When an Inventor decides to invent something he generally doesn’t know what it is he is going to create, unless of course he has already been inspired by an idea or a brain wave. Firstly he will try to think of something which everybody needs but hasn’t yet been thought of, this can be difficult and generally results in either a crazy device which nobody wants or something which quite simply is a brilliant idea but doesn’t work.
Another approach is to think of something that doesn’t exist and think of a way to make it work, a good example of this is an invisibility cloak, it works but nobody knows how; other than the inventor.
The inventor can think big and dream up something which has been deemed impossible and may even contradict all the laws of science, so he decides to do it. This latter approach is by far the best and most exciting option and is no doubt a challenge which starts to pump the adrenalin for any committed inventor. He will make it possible and make it happen.