Saw, that there is a spiffs.h lib in:
C:\Users\brutzler\AppData\Roaming\Arduino15\packages\esp8266\hardware\esp8266\1.6.5-947-g39819f0\cores\esp8266\spiffs
Regarding to this doc: https://github.com/esp8266/Arduino/blob/esp8266/hardware/esp8266com/esp8266/doc/reference.md#file-system I used some commands like SPIFFS.begin();
But I only get a 'SPIFFS' was not declared in this scope
Adding a #include "spiffs.h" --> fatal error: spiffs.h: No such file or directory
Hmm.....
ESP8266 Arduino add-on
Arduino IDE 1.6.5