Arduino Nano DetailsArduino Nano is a surface mount breadboard embedded version with integrated USB.
It is small, complete, and breadboard friendly. It has everything that Diecimila has (electrically) with more analog input pins and onboard +5V AREF jumper.
Physically, it is missing power jack and power select jumper.
Since the Nano is automatically sense and switch to the higher potential source of power, there is no need for the power select jumper.