The Arduino is, in our eyes, the perfect electronics platform at the hobbyist level. It's cheap, it's open, it's accessible, and it scales: there are Arduinos and compatibles ranging from a handful of components in a breadboard and the even more compact Arduino Pro Mini to the mainstream Arduino Uno and giant Arduino Mega. None of these models could ever be called speed demons, however - and they're not meant to be: they're powered by microcontrollers, not microprocessors, and value real-time operation over high compute performance. That isn't to say you can't squeeze some extra power out of the humble ATmega328, though, as Svarichevsky Mikhail proved back in 2013 by overclocking an Arduino Uno using liquid-nitrogen cooling. More readily associated with the extreme end of the enthusiast PC hobby, liquid nitrogen is extremely cold and a great - if very temporary - way of lowering the temperature of semiconductors like the ATmega328 in order to increase their stability at higher clock speeds. The result: the 16MHz Arduino reached 37MHz at room-temperature and 65.3MHz when submerged in liquid nitrogen. While it's not practical for everyday use, it's a cool experiment - if you'll pardon the pun - and also revealed some interesting LED behaviour at the extremely low temperatures used.
Overclocking microcontrollers with liquid nitrogen cooling promises to be harder than overclocking desktop processors: there are no stability tests, no on-board programmable frequency generator (at least on AVR microcontrollers), no programmable supply voltage. Also, it appeared that a number of on-board components were failing - so I had to deal with them individually. Luckily for me all these problems were sorted out at the end.