My favourite recent(-ish, 1927) bike development is the quick release skewers. So simple but damn useful. Invented by Tullio Campagnolo in 1927 after having difficulty while changing gears, which in ’27 involved removing the rear wheel and flipping it around to the the other gear on the other side. The wheels were held on by wing nuts and due to bad weather Tullio found it difficult to use the wing nuts, he lost time and his place in the race. I assume this greatly frustrated him, it would me, so he racked his mind and came up with a quick way of swapping wheels, the quick release skewers, it relies on the properties of cams. So now the invention has been used ever since, making wheel removal and installation much easier. Thank you Mr. Campagnolo for your invention, and also the parallelogram dérailleur, that’s pretty cool too.