The Micro-Rain-Radar MRR at 24 GHz is an unique meteorological radar profiler for Doppler spectra of hydrometeors in height ranges 15 m … 6000 m. The high resolution in time and height enables the MRR to monitor the genesis of frozen hydrometeors, the melting zone (bright band) and the formation of rain drops. With the derived rain rate the MRR offers a calibration of weather radar. The MRR has been adapted even for monitoring of avalanches and volcanos.