In the world of hardware, it’s only when you try and build something that you realise that ‘this’ will not connect to ‘that’ and that the ‘interface’ ( my internal nomenclature I’m using to describe it – ( subject to change ) ) introduces unwelcome weight/friction/stress/tension/geometry … constraints and renders an otherwise good design, infeasible. The answer really does seem to be a 3D printer, they really do solve the ‘interfacing this to that’ problem, albeit by introducing two constraints, restrictions on form and print material. Incidentally, I was reading that research is being undertaken in printing with Graphene … which is quite possibly worthy of the phrase ‘amazing’.
You don’t need a cake to make a cake, but it’s better to have a programming language to make another programming language or a robot to make another robot or a 3d printer to make another 3d printer or cell to make a cell … in this class of things reside all things that are supremely special.
You can add nuclear fission to that list and get to the idea of a chain reaction and uncover nature’s wonder weapon … exponential growth!