With the microSD-Shield the D1-Mini can be extended a storage possibility. Ideal for data logging. Pinout bulletpoint# 3.3 V: 3.3 V power supply bulletpoint# D8: SS (CS Chip Select) - D7: MOSI - D6: MISO bulletpoint# D5: CLK - GND: Ground Note:Delivery includes 2 pin headers (2x 8 Pin Male - Male)