Microcontroller board based on the ATmega32u4. With its small form factor, it's the ideal companion for your breadboard based projects.
It has 20 digital input/output pins (up to 7 can be used as PWM outputs and up to 12 as analog inputs), a 16MHz clock, a micro USB connection (which supports HID and CDC), TWI, SPI, UART interfaces, an ICSP header, and a reset button. Fully Arduino® compatible.
The board has all you need to get started, just plug in a USB cable and play!