Features:

–The Nano is a small, complete, and breadboard-friendly board based on the ATmega328 (Nano 3.x).
–The Nano can be powered via the Mini-B USB connection, 6-20V unregulated external power supply (pin 30), or 5V regulated external power supply (pin 27). The power source is automatically selected to the highest voltage source.
–The ATmega328 has 32 KB, (also with 2 KB used for the bootloader). The ATmega328 has 2 KB of SRAM and 1 KB of EEPROM.

–Specification–
Microcontroller：Atmel ATmega168 or ATmega328
Operating Voltage (logic level)：5 V
Input Voltage (recommended)：7-12 V
Input Voltage (limits)：6-20 V
Digital I/O Pins：14 (of which 6 provide PWM output)
Analog Input Pins：    8
DC Current per I/O Pin：40 mA
Flash Memory：16 KB (ATmega168) or 32 KB (ATmega328) of which 2 KB used by bootloader
SRAM：    1 KB (ATmega168) or 2 KB (ATmega328)
EEPROM：512 bytes (ATmega168) or 1 KB (ATmega328)
Clock Speed：16 MHz
Dimensions：0.73″ x 1.70″
Length：    45 mm
Width：    18 mm
Weigth：    5 g