We present a measurement technique that allows the determination of the velocity distribution of a micro-channel flow in the gas or liquid phase. Micro Particle-Image Velocimetry (μPIV) is a non-intrusive, laser-optical velocity measurement technique that is based on the determination of the displacement of small particles that are added to the flow. Especially in the gas phase μPIV strongly depends on particle characteristics like fluorescence, particle size distributions, and particle concentrations. The fidelity of the particles to adequately follow the flow is one of the key parameters of μPIV. The measurement technique is exemplarily applied in an optically transparent micro-channel with a 90° elbow to demonstrate the applicability of μPIV in a water flow as well as in a gaseous flow.