This is the successor to the popular Wemos ESP8266 D1 Mini. Sporting the new Expressif ESP32 dual core Wi-Fi and Bluetooth microcontroller. (Ironically this board is not manufactured by Wemos) Nonetheless, this is a super convenient board that's fully compatible with all the Wemos D1 Mini shields. Plus it has additional I/O provided by the beefier ESP32 on board. And when you put this board in a breadboard you appreciate it's space saving design. Like other ESP32 boards, this one blows away every possible comparison within the Arduino World. You must join the ESP32 revolution that has literally revolutionized the maker world.