The USB power may be the smallest in the series, but it's big enough to send juice to all your creations. Connect a USB cable (included) to your computer or phone charger to start the power flowing. Try it with an LED to make the simplest littleBits circuit. If you're looking for a permanent installation, the USB power adapter enables you to plug your USB power directly into the wall.
Using a USB connection to a computer, you have access to 500mA of power for your circuit. When using the USB Wall Adapter, you should have up to 1A of power available. The red LED shows you when the module is powered.