The Arduino Micro board is similar to the Arduino Leonardo, but much smaller -- one of Arduino's smallest board -- making it easy to integrate into everyday objects to make them interactive. By including a built-in USB communication, the Arduino Micro can appear as a mouse or keyboard to a connected computer, in addition to a virtual (CDC) serial or COM port.
The Micro is a microcontroller board based on the ATmega32U4 (datasheet), developed in conjunction with Adafruit.
It has 20 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs), a 16 MHz crystal oscillator, a micro USB connection, an ICSP header, and a reset button.
It contains everything needed to support the microcontroller; simply connect it to a computer with a micro USB cable to get started. It has a form factor that enables it to be easily placed on a breadboard.
The Micro board is similar to the Arduino Leonardo in that the ATmega32U4 has built-in USB communication, eliminating the need for a secondary processor.
The Micro can be powered via the micro USB connection or with an external power supply. The power source is selected automatically.