Considering the many folk tales of giants and dwarves, featuring in all sorts of cartoons, or toy trucks and model trains I played with a kid, it's interesting to think scaling in real life works very poorly - even going beyond such simple principles as the square-cube law, if you think about stuff like a pressure vessel with a certain wall thickness that needs to hold 100 bar - the thickness needed is the same regardless you have something the size of a golfball or a swimming pool.

This is imo why scaling down combustion engines beyond a certain point makes little sense - you don't gain anything in terms of weight since the wall thicknesses are determined by the pressures the engine has to endure which is the same - this is why model engines suck - they're not only less powerful than big ones, but less powerful per pound.