The Arduino Nano is Arduino's classic breadboard friendly designed board with the smallest dimensions. The Arduino Nano comes with pin headers that allow for an easy attachment onto a breadboard and features a Mini-B USB connector.
The classic Nano is the oldest member of the Arduino Nano family boards. It is similar to the Arduino Duemilanove but made for the use of a breadboard and has no dedicated power jack. Successors of the classic Nano are for example the Nano 33 IoT featuring a WiFi module or the Nano 33 BLE Sense featuring Bluetooth Low Energy and several environment sensors.
The ATMega328 CPU runs with 16 MHz and features 32 KB of Flash Memory (of which 2 KB used by bootloader).
With a length of 45 mm and a width of 18 mm the Nano is Arduino's smallest board and ways only 7 grams.
The Nano is made for breadboard use and features soldered headers for all pins, allowing to attach the board easily on any breadboard.