The Teensy is a complete USB-based microcontroller development system, in a very small footprint that is compatible with the Arduino ecosystem.
Teensy products are manufactured by PJRC.
Teensy Audio Adaptor Board for Teensy 3.X (Rev. C)
OctoWS2811 Adapter for Teensy (Controller for Neopixels/WS2811 LEDs)
Teensy 3.x Feather Adapter
SparkFun Qwiic Shield for Teensy
SparkFun Qwiic Shield for Teensy - Extended
PSRAM Chip for Teensy 4.1
Serial Flash Chip for Teensy 4.1 - 16MB/133 MHz, W25Q128JVSIQ
Teensy Header Kit