The Adafruit Gemma M0 is a super small microcontroller board, with just enough built-in to create many simple projects. It may look small and cute: round, about the size of a quarter, with friendly alligator-clip sew pads. But do not be fooled. The Gemma M0 is incredibly powerful.
The Gemma M0 has swapped out the lightweight ATtiny85 for a ATSAMD21E18 powerhouse.The Gemma M0 will super-charge your wearables! It's just as small, and it's easier to use.