The D1 mini is a mini wifi board based on ESP-8266EX.
Features:
- Microcontroller ESP-8266EX
- Operating Voltage 3.3V
- Digital I/O Pins 11
- Analog Input Pins 1(Max input: 3.2V)
- Clock Speed 80MHz/160MHz
- Flash 4M bytes
- Length 34.2mm
- Width 25.6mm
- Weight 3g
More information https://wiki.wemos.cc/products:retired:d1_mini_v3.0.0
Tutorial: