Only 13mm long, Tomu really puts the micro in microprocessor. It's fully open-source development board with the silabs Gecko EFM32HG309 processor, on a little board that can slot right into your computer or laptop USB A port (USB C users will need an adapter).

The board feature two tiny LEDs, and two capacitive-touch pads, as well as a native USB bootloader. While it was originally designed for 2-factor authentication, it's great for very tiny USB projects, ARM/Gecko experimentation or adding a basic input to your computer. Best of all, it's fully open source! Check out the GitHub repo with lots of examples, programming instructions and projects

Comes with one fully assembled Tomu