7-9V polarity protected DC or the micro USB connector to any 5V USB source ^^ CircuitPython now comes preloaded ^^ ATSAMD21G18 ARM Cortex M0 processor, clocked at 48 MHz and at 3.3V logic ^^ Built in USB so it has USB-to-Serial program & debug capability built in with no need for an FTDI-like chip ^^ 256K of FLASH (8x more than the Atmega328) and 32K of RAM (16x as much)