Atom Matrix, which has a size of only 24 x 24 mm, is the most compact development board in the M5Stack development kit series. It provides more GPIO pins and is very suitable for handy and miniature embedded device development. The main control adopts the ESP32-PICO-D4 chip, which comes integrated with Wi-Fi and Bluetooth technologies and has 4 MB of integrated SPI flash memory. The Atom board provides an infrared LED along with the 5 x 5 RGB LED matrix on the panel, a built-in IMU sensor (MPU6886), and a YH2.0 interface. A general-purpose programmable button is provided below the RGB LED matrix to enable users to add input support to their various projects. The on-board USB interface (Type-C) enables rapid program uploading and execution. One M2 screw hole is provided on the back for mounting the board.