The Micro measures 48 mm in length and 18 mm in width and weighs about 13 g. The Nano, on the other hand, comes in the smallest form factor Arduino offers , with the same 18 mm width but a shorter ...

Except, on the Micro, there is no actual serial bus involved in programming the Arduino, as everything is done over USB. So the TX and RX leds are driven by a couple of pins on the ATmega32U4 (see a ...